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Abstract:

Emissive quantum photonic imagers comprised of a spatial array of
digitally addressable multicolor pixels. Each pixel is a vertical stack
of multiple semiconductor laser diodes, each of which can generate laser
light of a different color. Within each multicolor pixel, the light
generated from the stack of diodes is emitted perpendicular to the plane
of the imager device via a plurality of vertical waveguides that are
coupled to the optical confinement regions of each of the multiple laser
diodes comprising the imager device. Each of the laser diodes comprising
a single pixel is individually addressable, enabling each pixel to
simultaneously emit any combination of the colors associated with the
laser diodes at any required on/off duty cycle for each color. Each
individual multicolor pixel can simultaneously emit the required colors
and brightness values by controlling the on/off duty cycles of their
respective laser diodes.

Claims:

1-47. (canceled)

48. An emissive multicolor digital image forming (imager) device
comprising;a two dimensional array of multicolor light emitting pixels
whereby each multicolor light emitting pixel comprises:a plurality of
light emitting diode semiconductor structures, each for emitting a
different color, stacked vertically with a grid of vertical sidewalls
electrically and optically separating each multicolor pixel from adjacent
multicolor pixels within the array of multicolor pixels; anda plurality
of vertical waveguides optically coupled to the light emitting diode
semiconductor structures to vertically emit light generated by the light
emitting diode semiconductor structures from a first surface of the stack
of diode semiconductor structures;the stack of light emitting diode
semiconductor structures being stacked onto a digital semiconductor
structure by a second surface opposite the first surface of the stack of
light emitting diode semiconductor structures; anda plurality of digital
semiconductor circuits in the digital semiconductor structure, each
electrically coupled to receive control signals from the periphery of the
digital semiconductor structure and electrically coupled to the
multicolor light emitting diode semiconductor structures by vertical
interconnects embedded within the vertical sidewalls to separately
control the on/off states of each of the multicolor light emitting diode
semiconductor structures.

49. The device of claim 48 wherein each light emitting diode semiconductor
structure has a metal layer on the top and bottom thereof, the metal
layers on adjacent light emitting diode semiconductor structures being
separated by an insulation layer between the respective metal layers.

50. The device of claim 49 wherein the metal layers provide positive and
negative contacts with each of the stacked light emitting diode
semiconductor structures.

51. The device of claim 50 further comprising a patterned interconnect
layer of metal isolated from the metal layers with a patterned insulation
layer and connected to the vertical interconnects to provide contact pads
for interconnecting the digital semiconductor structure with each of the
light emitting diode semiconductor structures in the two dimensional
array of multicolor light emitting pixels.

52. The device of claim 51 wherein each light emitting diode semiconductor
structure is separately addressable through the contact pads.

53. The device of claim 48 wherein the vertical sidewalls with vertical
interconnects therein comprise alternate layers of insulation and metal
surrounding each pixel, whereby the optical separation provided by the
metal layers around each pixel is uninterrupted.

55. The device of claim 54 wherein the composition of the semiconductor
layers enable each of the light emitting diode semiconductor structures
to generate light with a wavelength within the range of visible light
including 430-nm to 650-nm.

57. The device of claim 54 wherein the vertical waveguides are optically
coupled to each of the optical confinement regions of the light emitting
diode semiconductor structures.

58. The device of claim 48 wherein the vertical waveguides are comprised
of a core and a multilayer cladding, the core being either filled with
dielectric material or is air-filled.

59. The device of claim 58 wherein each light emitting diode semiconductor
structure comprises an active region and an optical confinement region,
the multilayer cladding being comprised of an outer cladding layer of
dielectric material and an inner thin cladding layer of reflective
metallic material, the thickness of the inner thin cladding material
being selected to allow a portion of the light generated by the active
regions of the light emitting diode semiconductor structures and confined
within the confinement regions to be evanescence field coupled into the
cores of the vertical waveguides and emitted vertically from the surface
of the two dimensional array.

60. The device of claim 58 wherein each light emitting diode semiconductor
structure comprises an active region and an optical confinement region,
the multilayer cladding being comprised of multiple thin layers of
dielectric material, the refractive indices of the core and the multiple
thin cladding layers and the thickness of the multiple cladding layers
being selected to allow a portion the light generated by the active
regions and confined within the confinement regions to be coupled into
the cores of the vertical waveguides and be index guided and emitted
vertically from the surface of the two dimensional array.

61. The device of claim 58 wherein each light emitting diode semiconductor
structure comprises an active region and an optical confinement region,
the multilayer cladding comprising a thin layer of nonlinear optical
material having its thickness and linear and nonlinear refractive indices
selected to cause the coupling of the light generated by the active
regions and confined within the confinement regions to be either
inhibited or enabled as the refractive index of the thin nonlinear
cladding layer changes in response to the changes in the intensity of the
light being confined within the confinement regions, thereby causing the
light being coupled into and index guided by the vertical waveguides and
emitted vertically from the surface of the two dimensional array to occur
in short pluses separated by short intervals.

62. The device of claim 48 wherein each light emitting diode semiconductor
structure comprises an active region and an optical confinement region,
each vertical waveguide having a circular cross section with an index
guiding diameter at the center of the coupling region within each of the
confinement regions of the light emitting diode semiconductor structures
equal to the wavelength of the light generated by the respective active
region.

63. The device of claim 48 wherein each light emitting diode semiconductor
structure comprises an active region and an optical confinement region,
and wherein for each light emitting diode semiconductor structure, at
least one vertical waveguide extends from the first surface of the stack
of light emitting diode semiconductor structures and terminates at the
end of the optical confinement region of that light emitting diode
semiconductor structure.

64. The device of claim 48 wherein the vertical waveguides are arranged in
a pattern selected to reduce the maximum divergence angle of the light
emitted from surface of the two dimensional array.

65. The device of claim 48 wherein the vertical waveguides are spaced
within the pixel surface area to provide uniform brightness across each
pixel area and provided in number to maximize pixel brightness.

66. The device of claim 48 wherein the light emitting diode semiconductor
structures comprise:multiple semiconductor layers of one or more of the
following semiconductors alloy materials:AlxIn1-XP,
(AlxGa1-x)yIn1-yP, GaxIn1-xP,
AlxGa1-xN, AlxGa1-xN/GaN, InxGa1-xN,
GaN;each formed on a separate wafer over a thick substrate layer of
either GaAs, GaN or InGaN;each including an n-type etch-stop layer and a
p-type contact layer of the same respective semiconductor substrate layer
material type;each comprising n-type and p-type waveguide layers and
cladding layers that define their respective optical confinement
regions;each having at least one quantum well surrounded by two barrier
layers that define their respective active regions; andeach comprising an
electron blocker layer embedded either within their respective p-type
waveguide layers or between their respective p-type waveguide and
cladding layers.

67. The device of claim 48 wherein the digital semiconductor structure is
responsive to serial bit streams that are serial representations of
multiple bit words that each define a color component and brightness of
respective pixels to convert a source digital image data input into an
optical image whereby each of the multicolor pixels emits light having
color and brightness that reflects the color and brightness values
represented by source digital image input data of the respective pixel.

68. The device of claim 48 further comprising a companion device to
receive image source data and convert the image source data into the
on-off duty cycle values of light emitting diodes comprising each of the
pixels of the emissive multicolor image forming device, the companion
device including:a color-space conversion block;a uniformity correction
block, including a weighting factor look-up table;a pulse-width
modulation conversion block; anda synchronization and control block;the
weighting factor look-up table storing brightness uniformity weighting
factors for each color of each pixel determined by a device-level test in
which brightness of the pixel array comprising the emissive aperture is
measured and a brightness uniformity weighting factor is calculated for
each light color for each pixel.

69. The device of claim 68 wherein the device is configured to receive
serial data streams for each color light emitting diode and control
signals for on-off duty cycle control of each light emitting diode in the
array of stacked light emitting diode semiconductor structures, the
companion device being configured to provide serial data streams for each
color light emitting diode and control signals for on-off duty cycle
control of each light emitting diode in the array of stacked light
emitting diode semiconductor structures.

70. The device of claim 48 wherein each two dimensional array of
multicolor light emitting pixels is cut from a wafer of multiple two
dimensional arrays of multicolor light emitting pixels, and each digital
semiconductor structure is cut from a wafer of multiple digital
semiconductor structures, each two dimensional array of multicolor light
emitting pixels being die-level bonded to a respective digital
semiconductor structure.

71. An emissive digital image forming (imager) device comprising;a two
dimensional array of light emitting pixels on a first semiconductor
substrate, the light emitting pixels being separated by a grid of
vertical sidewalls electrically and optically separating the light
emitting pixels:the first semiconductor substrate being stacked onto a
digital semiconductor structure by a second surface opposite the first
surface of the first semiconductor substrate; anda plurality of digital
semiconductor circuits in the digital semiconductor structure, each
electrically coupled to receive control signals and electrically coupled
to the light emitting pixels on the first semiconductor substrate by
vertical interconnects embedded within the vertical sidewalls to
separately control the on/off states of each of the diode semiconductor
structures.

[0003]The present invention relates to emissive imager devices comprising
a monolithic semiconductor arrays of multicolor laser emitters that can
be used as an image sources in digital projection systems.

[0004]2. Prior Art

[0005]The advent of digital display technology is causing a phenomenal
demand for digital displays. Several display technologies are poised to
address this demand; including Plasma Display Panel (PDP), Liquid Crystal
Display (LCD), and imager based projection displays that use
micro-mirrors, a liquid crystal on silicon (LCOS) device or a high
temperature poly-silicon (HTPS) device (Ref. [33]). Of particular
interest to the field of this invention are projection based displays
that use imager devices, such as those mentioned, as an image forming
device. These types of displays are facing strong competition from PDP
and LCD displays and as such are in critical need for effective means to
improve their performance while significantly reducing their cost. The
primary performance and cost driver in these types of displays are the
imagers used, such as micro-mirrors, LCOS and HTPS devices. Being passive
imagers, such devices require complex illumination optics and end up
wasting a significant part of the generated light, which degrades the
performance and increases the cost of the display system. The objective
of this invention is to overcome the drawbacks of such imager devices by
introducing an emissive imager device which comprises an array of
multicolor laser emitters that can be used as an image source in digital
projection systems.

[0006]FIGS. 1A and 1B are block diagram illustrations of typical projector
architectures 100 used in projection display systems that use a passive
imagers, such as those that use reflective imagers including
micro-mirrors or LCOS imager devices (FIG. 1A) and those that use a
transmissive imager, such as HTPS imager devices (FIG. 1B); respectively.
In general, the projector 100 of a typical projection display system of
FIG. 1A is comprised of an imager 110, illuminated by the illumination
optics 120 which couples the light generated by the light source 130 onto
the surface of the imager 120. The light source 130 can either be a lamp
that generates white light or a semiconductor light source, such as light
emitting diodes (LED) or laser diodes, that can generate Red (R), Green
(G) or Blue (B) light.

[0007]In the case of the projector 100 that uses a reflective imager
illustrated in FIG. 1A, when a lamp is used as a light source, a color
wheel incorporating R, G and B filters is added between the illumination
optics and the imager to modulate the required color. When a
semiconductor light source is used in conjunction with a reflective
imager, the color is modulated by turning on the semiconductor light
source device having the required color, being either R, G or B.

[0008]In the case of a projector 100 that uses the transmissive imager
illustrated in FIG. 1B, when a lamp is used as a light source, the
illumination optics 120 includes optical means for splitting the
white-light generated by the lamp into R, G and B light patches that
illuminate the backsides of three HTPS imager devices and a dichroic
prisms assembly is added to combine the modulated R, G and B light and
couple it on the projection optics 140.

[0009]The projection optics 140 is optically coupled to the surface of the
imager 110 and the drive electronics 150 is electrically coupled to the
imager 110. The optical engine generates the image to be projected by
modulating the intensity of the light generated by the light source 130,
using imager 110, with the pixel grayscale input provided as image data
to the drive electronics 150. When a reflective imager (FIG. 1A) such as
micro-mirror or LCOS imager device is used, the drive electronics
provides the pixel grayscale data to the imager 110 and synchronizes its
operation either with the sequential order of the R, G and B segments of
the color wheel, when a white light lamp is used as a light source, or
with the sequential order in which the R, G or B semiconductor light
source is turned on. When a transmissive imager such as the HTPS imager
device is used, the drive electronics provides the pixel grayscale data
to the imager 110 and synchronizes the operation of each of the R, G and
B HTPS imager devices in order to modulate the desired color intensity
for each pixel.

[0010]Typically the losses associated with the coupling of light onto the
surface of imager 110 are significant because they include the intrinsic
losses associated with the imager 110 itself, such as the device
reflectivity or the transmissivity values, plus the losses associated
with collecting the light from the light source 130, collimating,
filtering and relaying it to the surface of the imager 110. Collectively
these losses can add up to nearly 90%; meaning that almost 90% of the
light generated by the light source 130 would be lost.

[0011]In addition, in the case of a reflective imager 110 such as
micro-mirror or LCOS imager devices, the imager 110 being comprised of a
spatial array of reflective pixels, sequentially modulates the respective
colors of the light coupled onto its pixelated reflective surface by
changing the reflective on/off state of each individual pixel during the
time period when a specific color is illuminated. In effect, a typical
prior art reflective imager can only modulate the intensity of the light
coupled onto its pixelated reflective surface, a limitation which causes
a great deal of inefficiency in utilizing the luminous flux generated by
the light source 130, introduces artifacts on the generated image, adds
complexities and cost to the overall display system and introduces yet
another source of inefficiency in utilizing the light generated by the
light source 130. Furthermore, both the reflective as well as the
transmissive type imagers suffer from an effect known as "photonic
leakage" which causes light to leak onto the off-state pixels, which
significantly limits the contrast and black levels that can be achieved
by these types of imagers.

[0012]As stated earlier, the objective of this invention is to overcome
the drawbacks of prior art imagers by introducing an emissive imager
device comprising an array of multicolor laser emitters that can be used
as an image source in digital projection systems. Although semiconductor
laser diodes have recently become an alternative light source 130 (Ref.
[1]-[4]) for use in projectors 100 of FIG. 1A to illuminate reflective
imagers 110 such as the micro-mirror imager device, the use of
semiconductor laser diodes as a light source does not help in overcoming
any of the drawbacks of prior art imagers discussed above. In addition
numerous prior art exists that describes projection displays that uses a
scanned laser light beam to generate a projection pixel (Ref. [5]-[6]).

[0013]Prior art Ref. [7] describes a laser image projector comprising a
two dimensional array of individually addressable laser pixels, each
being an organic vertical cavity laser pumped by an organic light
emitting diode (OLED). The pixel brightness of the laser image projector
described in prior art Ref. [7] would be a small fraction of that
provided by the pumping light source, which, being an OLED based light
source, would not likely to offer an ample amount of light, rendering the
brightness generated by the laser projector of prior art Ref. [7] hardly
sufficient to be of practical use in most projection display
applications.

[0014]Although there exist numerous prior art references that describe
laser arrays (Ref. [8]-[30]), no prior art was found that teaches the use
of multicolor laser emitters as pixels in an imager device. As it will
become apparent in the following detailed description, this invention
relates a separately addressable array of multicolor laser pixels formed
by optically and electrically separating a monolithic layered stack of
laser emitting semiconductor structures. With regard to creating an
optically and electrically separated (isolated) semiconductor laser
emitter array, Ref. [10] teaches methods for forming a single wavelength
laser semiconductor structure with isolation regions (i.e. physical
barriers) between the light emitting regions formed by either removing
material between the light emitting regions or by passivating the regions
between the light emitters of the semiconductor structure. However, the
methods described in Ref. [10] could only be used to create a
one-dimensional linear array of separately addressable single wavelength
laser emitters within the range of wavelength from 700 to 800 nm.

[0016]Although Ref. [22] describes a display system that uses an array of
vertical cavity surface emitting laser (VCSEL) diodes, because of the
inherent size of the VCSEL diodes described in Ref. [22], the approach
described would tend to produce substantially large pixels size because
of the inherent size of the multiple color of VCSEL diodes it uses which
are arranged side-by-side in the same plane to form a pixel array,
rendering it not usable as an imager device.

[0017]Given the aforementioned drawbacks of currently available imager
devices, an imager that overcomes such weaknesses is certain to have a
significant commercial value. It is therefore the objective of this
invention to provide an emissive imager device comprising a monolithic
semiconductor 2-dimensional array of multicolor laser emitters that can
be used as an image source in digital projection systems. Additional
objectives and advantages of this invention will become apparent from the
following detailed description of a preferred embodiments thereof that
proceeds with reference to the accompanying drawings.

[0094]References in the following detailed description of the present
invention to "one embodiment" or "an embodiment" means that a particular
feature, structure, or characteristics described in connection with the
embodiment is included in at least one embodiment of the invention. The
appearances of the phrase "in one embodiment" in various places in this
detailed description are not necessarily all referring to the same
embodiment.

[0095]An emissive imager is described herein. In the following
description, for the purpose of explanation, numerous specific details
are set forth in order to provide a thorough understanding of the
invention. It will be apparent, however, to one skilled in the art that
the invention can be practiced with different specific details. In other
instance, structures and devices are shown in block diagram form in order
to avoid obscuring the invention.

QPI Architecture--

[0096]The emissive multicolor digital image forming device described
herein, referred to as "Quantum Photonic imager" (QPI), is a
semiconductor device comprising a monolithic array of multicolor laser
emitters. The Quantum Photonic imager of this invention is comprised of a
plurality of emissive multicolor pixels whereby in one embodiment, each
pixel comprises a stack of red (R), green (G) and blue (B) light emitting
laser diodes. The multicolor laser light of each said pixel is emitted
perpendicular to the surface of the Quantum Photonic imager device via a
plurality of vertical waveguides that are optically coupled to the
optical confinement region of each the R, G and B laser diodes comprising
each pixel. The plurality of pixels that comprise the Quantum Photonic
imager devices are optically and electrically separated by sidewalls of
insulating semiconductor material embedded in which are the electrical
interconnects (vias) that are used to route electrical current to the
constituent laser diodes of each pixel. Each of the plurality of pixels
that comprise the Quantum Photonic imager devices is electrically coupled
to a control logic circuit that routes (enable) the electric current
signal to each of its constituent red (R), green (G) and blue (B) laser
diodes. The drive logic circuits associated with the plurality of pixels
form a drive logic array that is bonded together with the stack of red
(R), green (G) and blue (B) laser diodes to form a monolithic array of
multicolor laser pixels and drive circuitry.

[0097]FIGS. 2A, 2B and 2C illustrate a preferred embodiment of the Quantum
Photonic Imager device 200 of this invention. FIG. 2A illustrates an
isometric view of the Quantum Photonic imager device 200, while FIG. 2B
illustrates and isometric view of one of its constituent pixels 230 and
FIG. 2c is a top view illustration that shows the array of pixels 230
comprising the Quantum Photonic imager device 200 and the digital control
logic 229 positioned at the periphery of the pixel array.

[0098]As illustrated in FIG. 2A, the Quantum Photonic imager device 200
would be comprised of two semiconductor structures; namely the photonic
semiconductor structure 210 and the digital semiconductor structure 220.
The semiconductor structures 210 and 220 are bonded together either
through die-level bonding or wafer-level bonding to form the Quantum
Photonic imager device 200 illustrated in FIG. 2A. Each of the two
semiconductor structures comprising the Quantum Photonic imager device
200 is further comprised of multiple semiconductor layers. As illustrated
in FIG. 2A, the digital semiconductor structure 220 of the Quantum
Photonic imager device 200 would typically be larger in surface area than
the photonic semiconductor structure 210 to allow for the placement of
the digital control logic 229 and the bonding pads 221, through which the
power and image data signals are provided to the device, to be accessible
at the topside of the device. The photonic semiconductor structure 210 is
comprised of a plurality of emissive multicolor pixels and digital
semiconductor structure 220 is comprised of the digital drive logic
circuits that provide power and control signals to the photonic
semiconductor structure 210.

[0099]FIG. 2B is a cutaway isometric illustration of the semiconductor
structure of one of the pixels 230 comprising the Quantum Photonic imager
device 200 of one embodiment of this invention. As illustrated in FIG.
2B, each of the pixels 230 would have a sidewall 235 that provides
optical and electrical separation between adjacent pixels. As will be
explained in more detail in subsequent paragraphs, the electrical
interconnects required to supply power signals to the photonic
semiconductor structure 210 portion of the pixels 230 would be embedded
within the pixel sidewalls 235.

[0100]As illustrated in the pixel isometric cutaway view of FIG. 2B, the
portion of the photonic semiconductor structure 210 within the interior
of the pixels 230 would be comprised of the semiconductor substrate 240,
a red (R) laser diode multilayer 231, a green (G) laser diode multilayer
232 and a blue (B) laser diode multilayer 233 stacked vertically. The
laser light of each of the pixels 230 comprising the Quantum Photonic
imager device 200 would be emitted in a direction that is perpendicular
to the plane of the device top surface, hereinafter referred to as the
vertical direction, through the plurality of vertical waveguides 290,
each of which is optically coupled to the optical resonator (or the
optical confinement region) of each of the laser diodes 231, 232 and 233.
The plurality of vertical waveguides 290 would form a laser emitter array
that would define the laser light emission cross section (or optical
characteristics) of each of the pixels 230 comprising the Quantum
Photonic imager device 200 of this invention. The novel approach of this
invention of vertically stacking the laser diodes 231, 232 and 233 and
optically coupling the vertical waveguides 290 to the optical resonator
(or the optical confinement region) of each of the stacked laser diodes
231, 232 and 233 would enable multicolor laser light generated by these
laser diodes to be emitted through the array of vertical waveguides 290,
thus making the pixels 230 comprising the Quantum Photonic imager device
200 of this invention become emissive multicolor laser pixels.

[0101]FIG. 2c is a top view illustration of the Quantum Photonic imager
device 200 showing the top of the photonic semiconductor structure 210
comprising the 2-dimensional array of multicolor pixels 230 that forms
the emissive surface of the device and the top of the digital
semiconductor structure 220 extending beyond that of the photonic
semiconductor structure 210 to allow for the area required for the device
bonding pads 221 and the layout area for the device control logic 229.
The typical size of the pixels 230 of the preferred embodiment of the
Quantum Photonic Imager 200 of this invention would be in the range of
10×10 micron, making the emissive surface of a Quantum Photonic
imager device 200 that provides a VGA resolution (640×480 pixels)
be 6.4×4.8 mm. The actual size of the photonic semiconductor
structure 210 would extend beyond emissive surface area by few additional
pixels on each side, making the typical size of the photonic
semiconductor structure 210 be in the range of 6.6×5 mm and the
digital semiconductor structure 220 would extend beyond that area to
allow for the layout area of the control logic 229 and the device bonding
pads 221, making the typical dimensions of a Quantum Photonic imager
device 200 that provides a VGA resolution be in the range 7.6×6 mm.

[0102]Having described the underlying architecture of the Quantum Photonic
Imager devices 200 of this invention, the following paragraphs provide
detailed description of its constituent parts and manufacturing methods
thereof.

QPI Semiconductor Structure--

[0103]FIG. 3 is a cross-sectional view illustration of the semiconductor
multi structures that form the Quantum Photonic Imager Device 200 of this
Invention. The same reference numbers are used for the same items,
however the red, green and blue laser diodes semiconductor structures
prior to the formation of the pixels 230 would be referred to as the
multilayer laser diode structures 250, 260 and 270; respectively.

[0104]In accordance with the preferred embodiment of the fabrication
method of the Quantum Photonic Imager device 200 of this invention, the
multilayer laser diode structures 250, 260 and 270 would be fabricated
separately as semiconductor wafers using the appropriate semiconductor
processes, then post-processed to create the wafer-size multilayer stack
photonic semiconductor structure 210 that incorporates the metal and
insulation layers as illustrated in FIG. 3. The wafer-size multilayer
stack photonic semiconductor structure 210 would then be further
post-processed to create the pixels' sidewalls 235, which form the laser
diodes 231, 232 and 233, and the pixels' vertical waveguide 290 as
illustrated in FIG. 2B. Furthermore, the digital semiconductor structure
220 would also be fabricated separately as a semiconductor wafer using
the appropriate semiconductor processes, then wafer-level or die-level
bonded with the multilayer stack photonic semiconductor structure 210 to
create the Quantum Photonic Imager device 200 illustrated in FIG. 2A. The
following paragraphs describe the detailed design specifications of the
multilayer laser diode structures 250, 260 and 270 and the digital
semiconductor structure 220 as well as the detailed design specifications
of the wafers post-processing and fabrication flow required to create the
Quantum Photonic Imager device 200 of this invention.

[0105]The illustration of FIG. 3 shows the Quantum Photonic Imager device
200 being comprised of the semiconductor structures 210 and 220 with each
of these two semiconductor structures being further comprised of multiple
semiconductor layers. As illustrated in FIG. 3, the photonic
semiconductor structure 210 is comprised of a silicon (Si) substrate 240
and a stack of three multilayer laser diode structures 250, 260 and 270
separated by layers 241, 251, 261 and 271 of dielectric insulator, such
as silicon dioxide (SiO2), each preferably 150 to 200 nm-thick,
which provide top and bottom electrical insulation of each between the
three multilayer laser diode structures 250, 260 and 270.

[0106]Also incorporated within the photonic semiconductor structure 210
are the metal layers 252 and 253, which constitute the p-contact and
n-contact metal layers; respectively, of the red multilayer laser diode
250, the metal layers 262 and 263 which constitute the p-contact and
n-contact metal layers; respectively, of the green multilayer laser diode
260 and the metal layers 272 and 273 which constitute the p-contact and
n-contact metal layers; respectively, of the blue multilayer laser diode
270. Each of the metal layers 252, 253, 262, 263, 272 and 273 is
preferably 150 to 200 nm-thick of semiconductor interconnect
metallization layer having low electromigration and stress-migration
characteristics such as gold-tin (Au--Sn) or gold-titanium (Au--Ti)
multilayer metallization. The metallization layers 252, 253, 262, 263,
272 and 273 would also include a diffusion barrier that would prevent
excessive diffusion of the metallization layers into the insulation
layers 241, 252, 261 and 271.

[0107]As illustrated in FIG. 3, the interfaces between the semiconductor
structures 210 and 220 are the metal layer 282, at the photonic
semiconductor structure 210 side, and the metal layer 222 at the digital
control structure 220 side. Both of the metal layers 282 and 222 would be
etched to incorporate the electrical interconnect bonding pads between
the two semiconductor structures 210 and 220. The metal layer 222 would
also incorporate the device bonding pads 221.

[0108]The insulation layers 241, 251, 261 and 271 and metallization layers
252, 253, 262, 263, 272 and 273 would be deposited using typical
semiconductor vapor deposition process such as chemical vapor deposition
(CVD). The two layers 241 and 252 would be deposited directly on the Si
substrate layer 240, and the resultant multilayer stack 240-241-252 is
then wafer-level bonded to the p-layer of the red laser diode structure
250 using either direct wafer bonding, diffusion bonding or anodic
bonding techniques or the like.

[0109]The resultant semiconductor multilayer structure is then used as a
substrate upon which the layers 253, 251, and 262 would be deposited
using vapor deposition techniques such as CVD or the like and the
resultant multilayer stack 240-241-252-250-253-251-262 is then
wafer-level bonded to the p-layer of the green laser diode structures 260
using either direct wafer bonding, diffusion bonding or anodic bonding
techniques or the like, and the substrate on which the green laser diode
was formed is removed.

[0110]The resultant semiconductor multilayer structure is then used as a
substrate upon which the layers 263, 261, and 272 would be deposited
using vapor deposition techniques such as CVD or the like and the
resultant multilayer stack 240-241-252-250-253-251-262-260-263-261-272 is
then wafer-level bonded to the p-layer of the blue laser diode structures
270 using either direct wafer bonding, diffusion bonding anodic bonding
techniques or the like, and the substrate on which the blue laser diode
was formed is removed.

[0111]The resultant semiconductor multilayer structure is then used as a
substrate upon which the layers 273, 271, and 282 would be deposited
using vapor deposition techniques such as CVD or the like. The metal
layer 282 is then etched to create the bonding pad pattern using
semiconductor lithography process and the etched areas are refilled with
insulator material, preferably SiO2, and the surface is then
polished and cleaned. The resultant photonic semiconductor structure 210
is then wafer-level bonded to the corresponding bonding pad surface of
the digital semiconductor structure 220 using flip-chip bonding
techniques.

[0114]FIG. 4A illustrates an exemplary embodiment of the multilayer cross
section of the red laser diode structure 250 of the Quantum Photonic
imager device 200 of this invention. The multilayer semiconductor
structure of FIG. 4A is phosphide based with its parameters selected such
that the laser light generated by the red laser diode structure 250 would
have a dominant wavelength of 615-nm. As shown in FIG. 4A, a substrate
removal etch-stop layer 412 of n-doped GaAs of thickness 100-nm is grown
on a thick (approximately 2000 nm) GaAs substrate 410 which will be
etched off after the red laser diode structure 250 is wafer-level bonded
to the multilayer stack 240-241-252 as explained earlier. The n-doped
GaAs etch-stop layer 412 would have either silicon (Si) or selenium (Se)
doping of approximately 8×1018 cm-3. A thick GaAs
substrate is used to assure the growth of a high quality epi layer
thereon.

[0115]Upon the substrate removal etch-stop layer 412 is deposited the
cladding layer 414 of n-type of either Al0.5In0.5P or
(Al0.7Ga0.3)0.5In0.5 superlattice (SL) which would
typically be 120-nm thick and have either Si or Se doping of
1×1018 cm-3.

[0116]Upon the cladding layer 414 is deposited a 100-nm thick n-type
(Al0.55Ga0.45)0.5In0.5P waveguide layer 416 which
would typically be either silicon (Si) or selenium (Se) doped to at least
1×1018 cm-3. Upon the waveguide layer 416 is deposited
the active region 421 of the red laser diode 250 comprised of multiple
Ga0.6In0.4P quantum well layers 420 which are enclosed within
the Al0.5In0.5P barrier layers 418, typically either silicon
(Si) or selenium (Se) doped at levels of least 0.01×1018
cm-3 and 0.1×1018 cm-3, respectively. As shown in
FIG. 4A, the thickness of the quantum well layers 420 and barrier layers
418 are selected to be 4.8-nm and 4-nm; respectively, however the
thickness of these layers could be increased or decreased in order to
fine tune the emission characteristics of the red laser diode 250.

[0117]Although FIG. 4A shows the active region 421 of the red laser diode
250 being comprised of three quantum wells, the number of quantum wells
used could be increased or decreased in order to fine tune the emission
characteristics of the red laser diode 250. Furthermore, the active
region 421 of the red laser diode 250 could also be comprised of
multiplicity of quantum wires or quantum dots instead of quantum wells.

[0118]Above the active region 421 is deposited a 140-nm thick p-type
(Al0.55Ga0.45)0.5In0.5P waveguide layer 422 which
would typically be magnesium (Mg) doped at a level of at least
1×1018 cm-3. Upon waveguide layer 422 is deposited a
23-nm thick Al0.5In0.5P anti-tunneling layer 424 having a
magnesium doping level of at least 1×1018 cm-3. Upon
anti-tunneling layer 424 is deposited an electron blocker layer 426 of
thickness 25-nm which is comprised alternating layers of
Ga0.5In0.5P quantum wells and Al0.5In0.5P barriers
each being magnesium doped at a level of at least 1×1018
cm-3. The electron blocker layer 426 is incorporated in order to
reduce the electron leakage current, which would reduce the threshold
current and the operating temperature of the red laser diode structure
250.

[0119]Above the electron blocker layer 426 is deposited a 120-nm thick
p-type of either Al0.5In0.5P or
(Al0.7Ga0.3)0.5In0.5 SL cladding layer 428 which
would typically be magnesium doped at a level of 0.5×1018
cm-3. Upon the cladding layer 428 is deposited a 100-nm thick p-type
GaAs contact layer 429 which would heavily magnesium doped at a level of
at least 1×1018 cm-3. As explained earlier, the contact
layer 429 would be the interface layer for the wafer-level bonding of the
red laser diode structure 250 and the multilayer stack 240-241-252.

[0120]The multilayer 416-421-422 is known to a person skilled in the art
as the optical resonator or optical confinement region of the red laser
diode 250 within which the red laser light generated by the MQW active
region 421 would be confined. As will be explained in the subsequent
paragraphs, the light generated by the red laser diode 250 will be
emitted vertically from the surface of the Quantum Photonic imager device
200 through vertical waveguides 290 that are optically coupled to the
optical confinement multilayer 416-421-422 of the red laser diode 250.

[0121]Green Laser Diode

[0122]FIG. 4B illustrates an exemplary embodiment of the multilayer cross
section of the green laser diode structure 260 of the Quantum Photonic
imager device 200 of this invention. The multilayer semiconductor
structure of FIG. 4B is nitride based with its parameters are selected
such that the laser light generated by the green laser diode structure
260 would have a dominant wavelength of 520-nm. As shown in FIG. 4B, a
substrate removal etch-stop layer 432 of n-doped In0.05Ga0.95N
of thickness 100-nm and Si-doped at a level 6×1018 cm-3
is grown on a thick GaN substrate 430 which will be etched off after the
green laser diode structure 260 is wafer-level bonded to the multilayer
stack 240-241-252-250-53-251-262 as explained earlier. The n-doped
In0.05Ga0.95N etch-stop layer 432 would have silicon (Si)
doping of 6×1018 cm-3. Although FIG. 4B shows the
substrate 430 being GaN, InGaN material alloy could also be used for the
substrate 430.

[0123]Upon the substrate removal etch-stop layer 432 is deposited the
cladding layer 434 of n-type of Al0.18Ga0.82N/GaN SL which
would typically be 451-nm thick and have Si doping of 2×1018
cm-3. Upon the cladding layer 434 is deposited a 98.5-nm thick
n-type GaN waveguide layer 436 which would typically be Si-doped at a
level of 6.5×1018 cm-3. Upon the waveguide layer 436 is
deposited the active region of the green laser diode 260 which is
comprised of multiple In0.535Ga0.465N quantum well layers 450
each being Si-doped at a level of 0.05×1018 cm-3 and
enclosed within the In0.04Ga0.96N barrier layers 438 each being
Si-doped at a level of 6.5×1018 cm-3. As shown in FIG.
4B, the thickness of the quantum well layers 450 and barrier layers 438
are selected to be 5.5-nm and 8.5-nm; respectively, however the thickness
of these layers could be increased o decreased in order to fine tune the
emission characteristics of the green laser diode 260.

[0124]Although FIG. 4B shows the active region 431 of the green laser
diode 260 being comprised of three quantum wells, the number of quantum
wells used could be increased or decreased to in order to fine tune the
emission characteristics of the green laser diode 260. Furthermore, the
active region 431 of the green laser diode 260 could also be comprised of
multiplicity of quantum wires or quantum dots instead of quantum wells.

[0125]Above the active region 431 is deposited a 8.5-nm thick p-type GaN
waveguide layer 452 which would typically be magnesium (Mg) doped at a
level of 50×1018 cm-3. Upon waveguide layer 452 is
deposited a 20-nm thick Al0.2Ga0.8N electron blocker layer 454
having a magnesium (Mg) doping level of approximately 100×1018
cm-3. The electron blocker layer 454 is incorporated in order to
reduce the electron leakage current, which would reduce the threshold
current and the operating temperature of the green laser diode structure
260.

[0126]Above the electron blocker layer 454 is deposited a 90-nm thick
p-type GaN waveguide layer 456 which would typically be magnesium (Mg)
doped at a level of 75×1018 cm-3. Upon the waveguide
layer 456 is deposited a 451-nm thick p-type Al0.18Ga0.82N/GaN
SL cladding layer 458 which would typically be magnesium doped at a level
of 75×1018 cm-3. Upon the cladding layer 458 is deposited
a 100-nm thick p-type GaN contact layer 459 which is magnesium (Mg) doped
at a level of 75×1018 cm-3. As explained earlier, the
contact layer 459 would be the interface layer for the wafer-level
bonding of the green laser diode structure 260 and the multilayer stack
240-241-252-253-251-262.

[0127]The multilayer 436-431-452 is known to a person skilled in the art
as the optical resonator or optical confinement region of the green laser
diode 260 within which the green laser light generated by the MQW active
region 431 would be confined. As will be explained in the subsequent
paragraphs, the light generated by the green laser diode 260 will be
emitted vertically from the surface of the Quantum Photonic imager device
200 through vertical waveguides 290 that are optically coupled to the
optical confinement multilayer 436-431-452 of the green laser diode 260.

[0128]Blue Laser Diode

[0129]FIG. 4C illustrates an exemplary embodiment of the multilayer cross
section of the blue laser diode structure 260 of the Quantum Photonic
imager device 200 of this invention. The multilayer semiconductor
structure of FIG. 4C is nitride based with its parameters selected such
that the laser light generated by the blue laser diode structure 260
would have a dominant wavelength of 460-nm. As shown in FIG. 4C, a
substrate removal etch-stop layer 462 of n-doped In0.05Ga0.95N
of thickness 100-nm Si doped at a level 6×1018 cm-3 is
grown on a thick GaN substrate 460 which will be etched off after the
blue laser diode structure 270 is wafer-level bonded to the multilayer
stack 240-241-252-250-53-251-262-260-263-261-272 as explained earlier.
The n-doped In0.05Ga0.95N etch-stop layer 462 would have
silicon (Si) doping of 6×1018 cm-3. Although FIG. 4C
shows the substrate 460 being GaN, InGaN material alloy could also be
used for the substrate 460.

[0130]Upon the substrate removal etch-stop layer 462 is deposited the
cladding layer 464 of n-type of Al0.18Ga0.82N/GaN SL which
would typically be 451-nm thick and have Si doping of 2×1018
cm-3. Upon the cladding layer 464 is deposited a 98.5-nm thick
n-type GaN waveguide layer 466 which would typically be Si doped at a
level of 6.5×1018 cm-3. Upon the waveguide layer 466 is
deposited the active region of the blue laser diode 270 which is
comprised of multiple In0.41 Ga0.59N quantum well layers 470
each being Si-doped at a level of 0.05×1018 cm-3 and
enclosed within the In0.04Ga0.96N barrier layers 468 each being
Si-doped at a level of 6.5×1018 cm-3. As shown in FIG.
4C, the thickness of the quantum well layers 470 and barrier layers 468
are selected to be 5.5-nm and 8.5-nm; respectively, however the thickness
of these layers could be increased or decreased in order to fine tune the
emission characteristics of the blue laser diode 270.

[0131]Although FIG. 4C shows the active region 431 of the green laser
diode 260 being comprised of three quantum wells, the number of quantum
wells used could be increased or decreased in order to fine tune the
emission characteristics of the green laser diode 260. Furthermore, the
active region 431 of the blue laser diode 260 could also be comprised of
multiplicity of quantum wires or quantum dots instead of quantum wells.

[0132]Above the active region 431 is deposited a 8.5-nm thick p-type GaN
waveguide layer 472 which would typically be magnesium (Mg) doped at a
level of 50×1018 cm-3. Upon waveguide layer 472 is
deposited a 20-nm thick Al0.2Ga0.8N electron blocker layer 474
having a magnesium (Mg) doping level of approximately 100×1018
cm-3. The electron blocker layer 474 is incorporated in order to
reduce the electron leakage current, which would reduce the threshold
current and the operating temperature of the blue laser diode structure
270.

[0133]Above the electron blocker layer 474 is deposited a 90-nm thick
p-type GaN waveguide layer 476 which would typically be magnesium (Mg)
doped at a level of 75×1018 cm-3. Upon the waveguide
layer 476 is deposited a 451-nm thick p-type Al0.18Ga0.82N/GaN
SL cladding layer 478 which would typically be magnesium (Mg) doped at a
level of 75×1018 cm-3.

[0134]Upon the cladding layer 478 is deposited a 100-nm thick p-type GaN
contact layer 479 which is magnesium doped at a level of
75×1018 cm-3. As explained earlier, the contact layer 479
would be the layer for the wafer-level bonding of the blue laser diode
structure 270 and the multilayer stack
240-241-252-253-251-262-260-263-261-272.

[0135]The multilayer 466-461-472 is known to a person skilled in the art
as the optical resonator or optical confinement region of the blue laser
diode 270 within which the blue laser light generated by the MQW active
region 461 would be confined. As will be explained in the subsequent
paragraphs, the light generated by the blue laser diode 270 will be
emitted vertically from the surface of the Quantum Photonic imager device
200 through vertical waveguides 290 that are optically coupled to the
optical confinement multilayer 466-461-472 of the blue laser diode 270.

[0136]An alternative exemplary embodiment of the multilayer red laser
diode structure 250 of the Quantum Photonic imager device 200 that is
nitride-based is illustrated in FIG. 4D. Being nitride-based, the
alternative exemplary embodiment of the multilayer red laser diode
structure 250 of FIG. 4D would have comparable design prescription as the
nitride-based green laser diode structure 260 of FIG. 4B and the blue
laser diode structure 270 of FIG. 4C, with the exception that its layer
parameters would be selected such that the generated laser light would
have a dominant wavelength of 615-nm. The alternative nitride-based
multilayer red laser diode structure 250 of FIG. 4D would be enabled by
the increase in the indium content of the multiple quantum wells 419 to
0.68. Although FIG. 4D shows its active region being comprised of three
quantum wells, the number of quantum wells used could be increased or
decreased in order to fine tune the emission characteristics of the red
laser diode 250. Furthermore, the active region of the alternative
exemplary embodiment of the red laser diode structure 250 illustrated in
FIG. 4D could also be comprised of multiplicity of quantum wires or
quantum dots instead of quantum wells. Although FIG. 4D shows the
substrate 480 being GaN, InGaN material alloy could also be used for the
substrate 480.

QPI Color Gamut--

[0137]As will be subsequently explained, the color gamut defined by the
three colors specified for the laser diodes 250, 260 and 270 in the
aforementioned exemplary embodiment of the Quantum Photonic Imager device
200 would achieve an extended gamut (Wide Gamut) relative to the defined
standards of color image displays such HDTV and NTSC. Specifically, the
three colors specified for the laser diodes 250, 260 and 270 in the
aforementioned exemplary embodiment of the Quantum Photonic Imager device
200 would achieve a color gamut that is nearly 200% of the color gamut
defined by the NTSC standard.

[0138]The color gamut achieved by the Quantum Photonic Imager device 200
of this invention can be further extended to include more than 90% of the
visible color gamut to achieve an Ultra-Wide Gamut capability by
increasing the number of laser diodes incorporated within the photonic
semiconductor structure 210 beyond the three colors specified for the
laser diodes 250, 260 and 270 in the aforementioned exemplary embodiment.
Specifically the color gamut of the light emitted by the Quantum Photonic
Imager device 200 could be extended further to achieve an Ultra-Wide
Gamut when the number of stacked laser diodes comprising the Quantum
Photonic Imager device 200 is increased to include yellow (572-nm) laser
diode semiconductor structure positioned in between the red and the green
laser diodes structure 250 and 260 and a cyan (488-nm) laser diode
semiconductor structure positioned in between the green laser diode
structure 260 and the blue laser diode structure 270, thus making the
Quantum Photonic Imager device 200 be comprised of a stack of five laser
diode structures covering the wavelengths of red (615-nm), yellow
(572-nm), green (520-nm), cyan (488-nm) and blue (460-nm). With this
stack of five laser diode semiconductor structures 210 of the Quantum
Photonic Imager device 200 of this invention would be able to generate an
Ultra-Wide color gamut that covers more than 90% of the visible color
gamut.

[0139]Although in the aforementioned exemplary embodiments of the photonic
semiconductor structure 210 of the Quantum Photonic Imager device 200,
the wavelengths of the laser diode structures 250, 260, and 270 were
selected to be 615-nm, 520-nm and 460-nm; respectively, a person skilled
in the art would know how to follow the teachings of this invention using
other values of wavelengths than those selected for the laser diode
structures 250, 260, and 270 of the aforementioned exemplary embodiments.
Furthermore, although in the aforementioned exemplary embodiments of the
Quantum Photonic Imager device 200, the photonic semiconductor structure
210 is comprised of the three laser diode structures 250, 260, and 270, a
person skilled in the art would know how to follow the teachings of this
invention using more than three laser diode structures. Furthermore,
although in the aforementioned exemplary embodiments of the Quantum
Photonic Imager device 200, the photonic semiconductor structure 210 is
comprised of the three laser diode structures 250, 260, and 270 stacked
in the order illustrated in FIG. 3, a person skilled in the art would
know how to follow the teachings of this invention with the laser diode
structures stacked in a different order.

[0140]Laser Diodes Energy Bands

[0141]FIG. 5A, FIG. 5B and FIG. 5C illustrate the energy bands of the
aforementioned exemplary embodiments of the phosphide based red laser
diode structure 250 and the nitride based green laser diode 260 and blue
laser diode 270; respectively. The energy bands shown in FIG. 5A, FIG. 5B
and FIG. 5C illustrate the thickness of each layer from left to right and
the energy from bottom to top. The thickness and energy levels are meant
to show qualitative values rather than a quantitative measure of the
exact thicknesses and energy levels. Nevertheless, the reference numbers
in FIG. 5A, FIG. 5B and FIG. 5C correspond with the reference numbers of
the layers in FIG. 4A, FIG. 4B and FIG. 4C; respectively. As these
figures illustrate, the energy levels of the p-type and n-type cladding
layers energetically confine the p-type and n-type waveguide layers as
well as the multiple quantum well levels. Because the energy levels of
the multiple quantum wells represent a local low energy level, as
illustrated in figures FIG. 5A, FIG. 5B and FIG. 5C, electrons will be
confined within the quantum wells to be efficiently recombined with the
corresponding holes to generate light.

[0142]In reference to FIG. 5A, the thickness of the anti-tunneling layer
424 is selected such that it is large enough to prevent electrons
tunneling yet small enough to retain electron coherence within the
superlattice structure of the electron blocker layer 426. In order to
lower the lasing threshold, the electron blocker layers 426, 454 and 474
are used in the exemplary embodiments of the laser diode structure 250,
260, and 270; respectively. As illustrated in FIG. 5A, the electron
blocker 426 used in the red laser structure 250 is comprised of multiple
quantum barriers (MQB) implemented in the p-doped region and having
energy level alternating between that of the waveguide layer 422 and the
cladding layer 428. The inclusion of the MQB electron blocker 426
substantially improves the electron confinement due to the quantum
interference of the electrons in the MQB, creating a large increase of
the barrier height at the waveguide-cladding layers interface, which
substantially suppresses the electron leakage current. As illustrated in
FIG. 5B and FIG. 5C, the electron blocker used in the green laser
structure 260 and the blue laser structure 270 is placed in between two
segments of the p-type waveguide layers and has energy level that is
substantially higher than both the waveguide layers as well as the
cladding layers in order to substantially improve the electron
confinement and subsequently suppresses the electron leakage current.

Pixel Sidewalls--

[0143]The plurality of pixels 230 that comprises the Quantum Photonic
imager device 200 are optically and electrically separated by the pixel
sidewalls 235 comprised of insulating semiconductor material and embedded
within which are the vertical electrical interconnects (contact vias)
that are used to route electrical current to the constituent laser diodes
of each pixel. FIG. 6A is a horizontal cross sectional view of one of the
plurality multicolor pixels 230 comprising the Quantum Photonic Imager
device 200 that illustrates the inner structure of the pixel sidewall
235. As illustrated in FIG. 6A, the pixel sidewall 235 defines the
boundaries of the multicolor pixel 230 and is comprised of the metal
contact vias 236 embedded within a sidewall interior 237 of dielectric
material such as SiO2.

[0144]FIG. 6B is a vertical cross-sectional view of one of the pixel
sidewalls 235 that illustrates the interface between the multilayer
photonic structure 210 and the sidewall 235. The pixel sidewalls 235
illustrated in FIG. 6A and FIG. 6B would be formed by etching an
orthogonal square grid of 1-micron wide trenches into the multilayer
photonic structure 210. The trenches would be etched at a pitch that
equals the pixel width, which in this exemplary embodiment of the Quantum
Photonic Imager device 200 is selected to be 10-micron, and at a depth
starting from the bonding pad layer 282 and ending at the SiO2
insulation layer 241. The etched trenches are then refilled with low
dielectric constant (low-k) insulating material such as SiO2 or
silicon carbon-doped silicon oxide (SiOC) then re-etched to form 150-nm
wide trenches for the contact vias 236. The re-etched trenches for the
contact vias 236 are then refilled using vapor deposition techniques,
such as CVD or the like, with metal such as gold-tin (Au--Sn) or
gold-titanium (Au--Ti) to achieve contact with the metallization layers
252, 253, 262, 263, 272 and 273.

[0145]The trenches etched for the pixel sidewalls 235 may have parallel
sides as illustrated in FIG. 6B or the may be slightly sloped as dictated
by the etching process used. Although any appropriate semiconductor
etching technique may be used for etching the trenches for the sidewalls
235 and the contact via 236, one exemplary etching technique is a dry
etching technique, such as chlorine-based, chemically-assisted ion beam
etching (Cl-based CAIBE). However, other etching techniques, such as
reactive ion etching (RIE) or the like may be used.

[0146]The formation of the pixel sidewalls 235 as described above is
performed in multiple intermediate stages during the formation of the
multilayer photonic structure 210. FIG. 6c is a vertical cross-sectional
view of the contact vias 236 embedded within the pixel sidewalls 235. As
illustrated in FIG. 6c, each of the contact vias 236 would be comprised
of the six segments 254 and 256 for the red laser diode structure 250
p-contact and n-contact; respectively, 264 and 266 for the green laser
diode structure 260 p-contact and n-contact; respectively, and 274 and
276 for the blue laser diode laser 270 p-contact and n-contact;
respectively.

[0147]After the multilayer structure 240-241-252-250 is formed as
explained earlier, the trench for the pixel sidewall 235 is double-etched
into the multilayer structure from the side of the red laser diode
multilayer 250 with the first and second stop-etch being below and above
the metal layer 252. The etched trench is then refilled with insulating
material such as SiO2 then retched with the stop-etch being the
metal layer 252 and refilled with contact metal material to form the base
segment of the contact via 254 as illustrated in FIG. 6c.

[0148]After the contact layer 253 and the insulation layer 251 are
deposited, the trench for the pixel sidewall 235 is double-etched into
the deposited layers with the first and second stop etch being below and
above the metal layer 253, refilled with insulating material, re-etched
with the stop-etch being the metal layer 253 and refilled with contact
metal material to form the base of the contact via 256 and to extend the
contact via 254 as illustrated in FIG. 6c.

[0149]After the contact layer 262 is deposited and the green laser diode
structure 260 is bonded with the multilayer structure, the trench for the
pixel sidewall 235 is double-etched into the formed multilayer structure
from the side of the green laser diode multilayer 250 with the first and
second stop-etch being below and above the metal layer 262. The etched
trench is then refilled with insulating material such as SiO2 then
retched with the stop-etch being the metal layer 262 and refilled with
contact metal material to form the base segment of the contact via 264
and extend the contact vias 254 and 256 as illustrated in FIG. 6c.

[0150]After the contact layer 263 and the insulation layer 261 are
deposited, the trench for the pixel sidewall 235 is double-etched into
the deposited layers with the first and second stop-etch being below and
above the metal layer 263, refilled with insulating material, re-etched
with the stop-etch being the metal layer 263 and refilled with contact
metal material to form the base segment of the contact via 266 and to
extend the contact vias 254, 256 and 264 as illustrated in FIG. 6c.

[0151]After the contact layer 272 is deposited and the blue laser diode
structure 270 is bonded with the multilayer structure, the trench for the
pixel sidewall 235 is double-etched into the formed multilayer structure
from the side of the green laser diode multilayer 250 with the first and
second stop-etch being below and above the metal layer 272. The etched
trench is then refilled with insulating material such as SiO2 then
retched with the stop-etch being the metal layer 272 and refilled with
contact metal material to form the base segment of the contact via 274
and extend the contact vias 254, 256, 264, and 266 as illustrated in FIG.
6C.

[0152]After the contact layer 273 and the insulation layer 271 are
deposited, the trench for the pixel sidewall 235 is double-etched into
the deposited layers with the first and second stop-etch being below and
above the metal layer 273, refilled with insulating material, re-etched
with the stop-etch being the metal layer 263 and refilled with contact
metal material to form the base segment of the contact via 276 and to
extend the contact vias 254, 256, 264, 266 and 274 as illustrated in FIG.
6C.

[0153]After the pixel sidewalls 235 are formed, the metal layer 282 would
be deposited then etched to create separation trenches between metal
contacts established with contact vias 254, 256, 264, 266, 274 and 276
and the etched trenches are then refilled with insulating material such
as SiO2 then polished to create the pixel contact pad 700 which is
illustrated in FIG. 7. The pixel contact pad 700 would form the contact
interface between the photonic semiconductor structure 210 and the
digital semiconductor structure 220.

Vertical Waveguides--

[0154]After the formation of the pixel sidewalls 235 as explained above,
the photonic semiconductor structure 210 would be partitioned by the
formed sidewalls 235 into electrically and optically separated square
regions that define the individual pixels 230 of the photonic
semiconductor structure. The formed photonic semiconductor structure of
each of the pixels 230 would then be comprised of a portion of the laser
diode semiconductor structures 250, 260 and 270 and will be designated
231, 232 and 233; respectively.

[0155]In addition to electrically and optically separating the multicolor
pixels 230 of the Quantum Photonic Imager device 200, the pixel sidewalls
235, being comprised of a dielectric material such as SiO2 with the
metal vias 236 illustrated in FIG. 6c embedded within its interior, would
also form optical barriers which would optically seal the vertical edges
of each of the portions of the optical confinement regions of the laser
diode structure 250, 260 and 270 comprising each multicolor pixel 230. In
other words, the insulation and metal contact layers in between the laser
diode structures 250, 260 and 270 together with the insulation and
contact vias within the pixels sidewalls 235 would form an array of
vertically stacked multicolor laser diode resonators that are optically
and electrically separated in the horizontal as well as the vertical
planes. Such an electrical and optical separation would minimize any
possible electrical or optical crosstalk between the pixels 230 and
allows each pixel within the array as well as each laser diode within
each pixel to be separately addressable. The laser light output from each
of the pixels 230 would be emitted vertically through the array of the
vertical waveguides 290 which are optically coupled to the optical
confinement regions of each of the vertically stacked laser diodes 231,
232, and 233 that form each of the pixels 230.

[0156]FIG. 8A and FIG. 8B illustrate vertical and horizontal
cross-sectional views; respectively, of one of the vertical waveguides
290 comprising the array of vertical waveguides of one of the pixels 230
of the Quantum Photonic Imager device 200 of this invention. As
illustrated in FIG. 8A and FIG. 8B, each of the vertical waveguides 290
would be optically coupled along its vertical height with optical
confinement regions of the three vertically stacked laser diodes 231,
232, and 233 comprising the pixel 230. As illustrated in FIG. 8A and FIG.
8B, each of the vertical waveguides 290 would be comprised of a waveguide
core 291 which would be enclosed within a multilayer cladding 292. The
array of pixel's waveguides 290 would typically be etched through the
Si-substrate 240 side of the photonic multilayer structure 210, their
interior would then be coated with the multilayer cladding 292 and the
waveguides would then be refilled with the dielectric material to form
the vertical waveguide core 291. Although any appropriate semiconductor
etching technique may be used for etching the vertical waveguides 290,
one exemplary etching technique is a dry etching technique, such as
chlorine-based, chemically-assisted ion beam etching (Cl-based CAIBE).
However, other etching techniques, such as reactive ion etching (RIE) or
the like may be used. Although any appropriate semiconductor coating
technique may be used for forming the core 291 and the multilayer
cladding 292 of the vertical waveguides 290, one exemplary layer
deposition technique is plasma-assisted chemical vapor deposition
(PE-CVD). The trenches etched for the vertical waveguides 290 preferably
will have slightly sloped sides as illustrated in FIG. 8A in accordance
with the increasing wavelength of the respective laser diodes in the
laser diode stack.

[0157]As illustrated in FIG. 8A and FIG. 8B, each of the vertical
waveguides 290 would typically have a circular cross-section and its
vertical height would extend the thickness of the Si-substrate 240 plus
the combined thicknesses of the three vertically stacked laser diodes
231, 232, and 233 comprising the pixel 230. Preferably the diameter
(index guiding diameter) of the pixel's vertical waveguides 290 at the
center of the coupling region with each of the laser diodes 231, 232, and
233 would equal to the wavelength of the respective laser diode.

First Embodiment of the Vertical Waveguides--

[0158]In one embodiment of the Quantum Photonic Imager device 200 of this
invention the cores 291 of the pixel's vertical waveguides 290 would be
"evanescence field coupled" to the optical confinement regions of stacked
laser diodes 231, 232, and 233 that form a single pixel 230. In this
embodiment the vertical waveguide cladding 292 would be comprised of an
outer layer 293 of 50-nm to 100-nm thick of insulating material, such as
SiO2, and an inner layer 294 of highly reflective metal such as
aluminum (Al), silver (Ag) or gold (Au). The core 291 of the vertical
waveguides 290 could either be air-filled or filled with a dielectric
material such as SiO2, silicon nitride (Si3N4) or tantalum
pentoxide (TaO5). Through the evanescence field coupling of this
embodiment, a fraction of the laser light confined within the optical
confinement region of each of the laser diodes 231, 232, and 233 would be
coupled into the dielectric core 291 of the vertical waveguides 290 where
it would be guided vertically through reflections on the highly
reflective metallic inner cladding layer 294 of the waveguide cladding
292.

[0159]In this embodiment of the Quantum Photonic Imager device 200 of this
invention the coupling between the optical confinement regions of stacked
laser diodes 231, 232, and 233 comprising each of the pixels 230 and its
constituent vertical waveguide 290 would occur due to photon tunneling
across the metallic inner cladding layer 294. Such photon tunneling would
occur when the thickness of the reflective metallic inner cladding layer
294 of the waveguide cladding 292 is selected to be sufficiently smaller
than the penetration depth of evanescence field into the reflective
metallic inner cladding layer 294 of the waveguide cladding 292. In other
words, the energy associated with the light confined within the optical
confinement regions of stacked laser diodes 231, 232, and 233 would be
transmitted into metallic inner cladding layer 294a short distance before
it returned into the optical confinement regions of stacked laser diodes
231, 232, and 233 and when the thickness of the reflective metallic layer
294 is sufficiently small, a portion of this energy would be coupled into
the vertical waveguide core 291 and would be guided vertically through
reflections on the highly reflective metallic inner cladding layer 294 of
the waveguide cladding 292 and emitted perpendicular to the surface of
the Quantum Photonic Imager device 200.

[0160]The evanescence field transmitted from the optical confinement
regions of stacked laser diodes 231, 232, and 233 into the reflective
metallic layer 294 would decay exponentially and would have mean
penetration depth "d" that is given by;

d=λ/2π {square root over (n02 sin2
θi-n12)} (1)

Where λ is the wavelength of the coupled light, n0 and n1
are the refractive index of the outer cladding layer 293 and the inner
cladding layer 294; respectively, and θi is the light angle of
incidence from optical confinement regions of the laser diodes 231, 232
and 233 onto the inner cladding layer 294.

[0161]As indicated by equation (1), for a given n0, n1 and
θi the evanescence field penetration depth decreases with the
decrease in the light wavelength λ. In order to use one thickness
value for the inner cladding layer 294 that would effectively couple the
three different wavelengths generated by the laser diodes 231, 232, and
233, the thickness of the inner cladding layer 294 would be selected
using Equation (1) with the value of λ being the wavelength
associated with shortest wavelength generated by stacked laser diodes
231, 232, and 233, being in the case of the aforementioned embodiment the
wavelength associated with the blue laser diode 233. When the thickness
of the inner cladding layer 294 is selected based on this criterion, the
light generated by the stacked laser diodes 231, 232, and 233 would be
coupled into the vertical waveguide 290 would be 0.492, 0.416 and 0.368;
respectively, of the intensity of the light reflected by the interface
between optical confinement region of stacked laser diodes 231, 232, and
233 and the vertical waveguide 290. When the thickness of inner cladding
layer 294 is increased, the amount of light coupled into the vertical
waveguide 290 will decrease proportionally. The reflectivity of the inner
cladding layer 294 toward the optical confinement regions of the laser
diodes 231, 232, and 233 and toward the vertical waveguide core 291 would
be given; respectively, by:

Where n2 is the refractive index of the vertical waveguide core 291
and k1 is the absorption coefficient of the inner cladding layer
294.

[0162]In the above exemplary embodiment of the evanescence field coupled
vertical waveguides 290 of this invention in which SiO2 is used as
an outer cladding layer 293 and Si3N4 is used as the waveguide
core 291 material, a 50-nm thick silver (Ag) inner cladding 294 would
couple approximately 36% of the laser light incident on the interface
between the optical confinement regions of the laser diodes 231, 232, and
233 and the vertical waveguide 290 while achieving approximately 62%
reflectivity within the interior of the vertical waveguides 290. It
should be noted that the part of the light which is not coupled into the
vertical waveguides 290 would either be absorbed by inner cladding 294
(approximately 0.025) or would be recycled back into the optical
confinement regions of the laser diodes 231, 232, and 233 where it would
be amplified by the active regions of laser diodes 231, 232, and 233 and
then re-coupled into the vertical waveguides 290.

Second Embodiment of the Vertical Waveguides--

[0163]In another embodiment of the Quantum Photonic Imager device 200 of
this invention the cores 291 of the pixel's vertical waveguides 290 would
be coupled to the optical confinement regions of stacked laser diodes
231, 232, and 233 that form a single pixel 230 through the use of
anisotropic multilayer thin cladding. What is meant by "anisotropic" in
this context is that the reflectance/transmittance characteristics would
be asymmetric at either side of the interface between the vertical
waveguide 290 and the optical confinement regions of the stacked laser
diodes 231, 232, and 233. The simplest realization of this embodiment
would be to use a single thin cladding layer 293 having a refractive
index value between that of the waveguide core 291 and the optical
confinement regions of laser diodes 231, 232, and 233 and having the
waveguide core 291 preferably filled with a dielectric material
preferably having a refractive index that is at least equal to that of
the optical confinement regions of the stacked laser diodes 231, 232, and
233.

[0164]The reflectance and transmittance characteristics of thin dielectric
multilayer coatings are described in detail in Ref. [39]. At a normal
angle of incidence, the reflectivity at the interface between the optical
confinement regions of laser diodes 231, 232, and 233 and the cladding
layer 293 would be given by:

R=[(n12-n0n1)/(n12+n0n1)]2
(3)

Where n0, n1 and n2 are the refractive index of the optical
confinement regions of stacked laser diodes 231, 232, and 233, of the
cladding layer 293 and the waveguide core 291; respectively. As the angle
of incidence at the interface between the optical confinement regions of
laser diodes 231, 232, and 233 and the cladding layer 293 increases, the
reflectivity increases until all the light is totally reflected when the
critical angle is reached. Since, the critical angle depends on the ratio
of the refractive index across the interface, when this ratio is selected
such that the critical angle of the interface between the optical
confinement regions of laser diodes 231, 232, and 233 and the cladding
layer 293 is larger than the critical angle between the waveguide core
291 and the cladding layer 293, a portion of the light would be coupled
into the waveguide core 291 and would be index guided through total
internal reflection (TIR) by the pixel's vertical waveguides 290 to be
emitted perpendicular to the surface of the Quantum Photonic Imager
device 200.

[0165]In the above exemplary embodiment of coupling of the vertical
waveguides 290 through the use of multilayer thin cladding in which an
approximately 100-nm thick of SiO2 is used as a cladding layer 293
and titanium dioxide (TiO2) is used as the waveguide core 291
material, approximately 8.26% of the laser light incident on the
interface between the optical confinement regions of the laser diodes
231, 232, and 233 and the vertical waveguide 290 would be coupled into
the waveguide core 291 and index guided through total internal reflection
by the pixel's vertical waveguides 290 to be emitted perpendicular to the
surface of the Quantum Photonic Imager device 200.

[0166]In comparison to the evanescence field coupling of the preceding
embodiment, coupling of vertical waveguides 290 through the use of
multilayer thin cladding would couple a lesser amount of the light from
the optical confinement regions of stacked laser diodes 231, 232, and 233
into the waveguide core 291, but the coupled light would not experience
any losses as it traverses the length of the vertical waveguide 290
because the light is TIR-guided, hence approximately the same amount of
the light would be outputted through the vertical waveguide 290
perpendicular to the surface of the Quantum Photonic Imager device 200.
It should be noted that the part of the light which is not coupled into
the vertical waveguides 290 by inner cladding 293 (which in the case of
this example would be 91.74%) would be recycled back into the optical
confinement regions of the laser diodes 231, 232, and 233 where it would
be amplified by the active regions of laser diodes 231, 232, and 233 and
then re-coupled into the vertical waveguides 290.

[0167]Although in the above exemplary embodiment of coupling of the
vertical waveguides 290 through the use of multilayer thin cladding only
a single layer was exemplified, multiple thin cladding layers could be
used to alter the ratio of the light intensity coupled into the vertical
waveguide 290 to that recycled back in the optical confinement regions of
the laser diodes 231, 232, and 233. For example when two thin cladding
layers are used with the outer cladding being 150-nm thick
Si3N4 and the inner cladding being 100-nm thick SiO2 in
conjunction a TiO2 waveguide core 291, approximately 7.9% of the
laser light incident on the interface between the optical confinement
regions of the laser diodes 231, 232, and 233 and the vertical waveguide
290 would be coupled into the waveguide core 291 and TIR-guided by the
pixel's vertical waveguides 290 to be emitted perpendicular to the
surface of the Quantum Photonic Imager device 200. The selection of the
number of thin cladding layers used, their refractive index and thickness
are design parameters that could be utilized to fine tune the coupling
characteristics of the pixel's vertical waveguides 290, and subsequently
the overall performance characteristics the Quantum Photonic Imager
device 200.

Third Embodiment of the Vertical Waveguides 290--

[0168]In another embodiment of the Quantum Photonic Imager device 200 of
this invention the core 291 of the pixel's vertical waveguides 290 would
be coupled to the optical confinement regions of stacked laser diodes
231, 232, and 233 that form a single pixel 230 through the use of
nonlinear optical (NLO) cladding. The primary advantage of this
embodiment is that it would enable the Quantum Photonic Imager device 200
of this invention to operate as a mode-locked laser emissive device
(mode-locking enables laser devices to emit ultra-short pluses of light).
As a consequence of the mode-locked operation the Quantum Photonic Imager
device 200 enabled by this embodiment, the Quantum Photonic Imager device
200 would achieve improved power consumption efficiency and a higher
peak-to-average emitted light intensity. The mode-locked operation of
this embodiment would be incorporated within the cladding 292 of the
pixel's vertical waveguides 290 in conjunction with the vertical
waveguide coupling method of the preceding embodiment.

[0169]This embodiment would be realized by adding a thin outer cladding
layer 295, herein after will be referred to as the gate cladding layer,
between the optical confinement regions of stacked laser diodes 231, 232,
and 233 and the outer cladding layer 293 as illustrated in FIG. 8B. The
gate cladding layer 295 would be a thin layer of an NLO material such as
single crystal poly PTS polydiacetylene (PTS-PDA) or polydithieno
thiophene (PDTT) or the like. The refractive index n of such NLO
materials is not a constant, independent of the incident light, but
rather its refractive index changes with increasing the intensity I of
the incident light. For such NLO materials, the refractive index n obeys
the following relationship to the incident light intensity:

n=n0+χ.sup.(3)I (4)

[0170]In Equation (4) χ.sup.(3) is the third order nonlinear
susceptibility of the NLO material and n0 is the linear refractive
index value that the NLO material exhibits for low values of the incident
light intensity I. In this embodiment the linear refractive index n0
and thickness of the NLO material comprising the gate cladding layer 295
are selected such that at low incident light intensity/, substantially
all of the light incident on the multilayer cladding 292 from the optical
confinement regions of stacked laser diodes 231, 232, and 233 would be
reflected back and recycled into the optical confinement regions of the
laser diodes 231, 232, and 233 where it would be amplified by the active
regions of laser diodes 231, 232, and 233.

[0171]As the light intensity within the optical confinement regions of the
laser diodes 231, 232, and 233 increases due to the integration light
flux, the refractive index n of the gate cladding layer 295 would change
in accordance with Equation (4), causing the ratio of the light intensity
that is recycled back into the optical confinement regions of the laser
diodes 231, 232, and 233 to that coupled into the vertical waveguide 290
to decrease, thus causing a portion of the light flux integrated within
the optical confinement regions of the laser diodes 231, 232, and 233 to
be coupled into the vertical waveguide 290 and emitted perpendicular to
the surface of the Quantum Photonic Imager device 200.

[0172]As the light is coupled into the waveguide 290, the integrated light
flux within the optical confinement regions of the laser diodes 231, 232,
and 233 would decrease, causing the intensity I of the light incident on
the gate cladding layer 295 to decrease, which in turn would cause the
refractive index n to change in accordance with Equation (4) causing the
ratio of the light intensity that is recycled back into the optical
confinement regions of the laser diodes 231, 232, and 233 to that that is
coupled into the vertical waveguide 290 to increase, thus causing the
cycle of light flux integration within the optical confinement regions of
the laser diodes 231, 232, and 233 to be repeated.

[0173]In effect the use of the multilayer cladding that incorporates an
NLO of this embodiment would cause the optical confinement regions of the
pixel's laser diodes 231, 232, and 233 to operate as photonic capacitors
which would periodically integrate the light flux generated by the
pixel's laser diodes 231, 232, and 233 between periods during which the
integrated light flux is coupled into the vertical waveguide 290 and
emitted at the surface of the pixel 230 of the Quantum Photonic imager
device 200.

[0174]When NLO gate cladding layer 295 is used in conjunction with the
multilayer thin cladding of the vertical waveguide 290 coupling examples
of the preceding embodiment, the coupling performance would be comparable
except that the light coupled into the vertical waveguide 290 and emitted
at the surface of the pixel 230 would occur as a train of pluses. When an
NLO gate cladding layer 295 of PTS-PDA having a thickness of
approximately 100-nm is used in conjunction with an approximately 100-nm
thick of SiO2 inner cladding 293 and titanium dioxide (TiO2) is
used as the waveguide core 291 material, the light pulses emitted from
the surface of the pixel 230 would typically have a duration in the range
of approximately 20-ps to 30-ps with an inter-pulse period in the range
of approximately 50-ps to 100-ps. The selection of the number of thin
cladding layers used in conjunction with NLO gate cladding layer 295,
their refractive index and thicknesses are design parameters that could
be utilized to fine tune the coupling characteristics of the pixel's
vertical waveguides 290 as well as the pulsing characteristics of the
multicolor laser light emitted from the pixel 230 and subsequently the
overall performance characteristics the Quantum Photonic Imager device
200.

Fourth embodiment of the Vertical Waveguides 290--

[0175]A fourth embodiment of vertical waveguides 290 may be seen in FIG.
2D. In this embodiment, waveguides terminate at the end of the optical
confinement region of each laser diode, so that the waveguides
terminating at the laser diode positioned at the top of the stack would
couple light only from that laser diode and the waveguides terminating at
the second from the top laser diode in the stack would couple light from
first and second laser diodes and the waveguides terminating at the third
laser diode from the top of the stack would couple light from the first,
second and third laser diodes in the stack. Preferably these waveguides
would be straight, not tapered. These waveguides may also be air filled
or filled with a suitable dielectric, such as SiO2. Using these
differing height waveguides the amount of light coupled from the first
laser diode in the stack would be higher than that coupled from the
second laser diode in the stack and the amount of light coupled from the
second laser diode in the stack would be higher than that coupled from
the third laser diode in the stack. Since a satisfactory color gamut
would include more green than red, and more red than blue, one might
place the green diode on top, the red in the middle and the blue on the
bottom of the stack.

Pixel Waveguide Array--

[0176]As explained in the preceding discussion, each of the pixels 230
comprising the Quantum Photonic Imager device 200 would comprise a
plurality of vertical waveguides 290 through which the laser light
generated by the pixel's laser diodes 231, 232, and 233 would be emitted
in a direction that is perpendicular to the surface of the Quantum
Photonic Imager device 200. The plurality of pixel's vertical waveguides
290 would form an array of emitters through which the light generated the
pixel's laser diodes 231, 232, and 233 would be emitted. Given the
vertical waveguides 290 light coupling methods of the preceding first
three embodiments, the light emitted from each of the pixel's vertical
waveguides 290 would have a Gaussian cross-section having an angular
width of approximately ±20 degrees at half its maximum intensity. In
the preferred embodiment of the Quantum Photonic Imager device 200, the
plurality of the pixel's vertical waveguides 290 would be arranged in a
number and a pattern that is selected to reduce the maximum divergence
angle (collimation angle) of the light emitted from surface of the pixel
230, to provide a uniform brightness across the area of the pixel, and to
maximize pixel brightness.

[0177]In using well known theories of phased emitter arrays Ref. [41], the
angular intensity of the light emitted by the pixels 230 within the
meridian plane comprising N of the pixel's vertical waveguides 290 would
be given by;

I(θ)=E(θ){J1[aX(θ)]/aX(θ)}2{Sin
[NdX(θ)]/Sin [dX(θ)]}2 (5.a)

Where;

X(θ)=(π Sin θ)/λ (5.b)

[0178]J1(.) the Bessel function, λ is the wavelength of the
light emitted by the pixel's vertical waveguides 290, a is the diameter
of the vertical waveguides 290, d is the center-to-center distance
between the pixel's vertical waveguides 290 and E(θ) is the
intensity profile of the light emitted from each the pixel's vertical
waveguides 290, which as stated earlier would typically be a Gaussian
profile having an angular width of approximately ±20 degrees at half
its maximum intensity. Preferably the parameter a, the diameter (index
guiding diameter) of the pixel's vertical waveguides 290 at the center of
the coupling region with each of the laser diodes 231, 232, and 233 would
equal to the wavelength of the respective laser diode. The typical value
of the parameter d, the center-to-center distance between the pixel's
vertical waveguides 290, would be at least 1.2a and its specific value
would be selected to fine tune emission characteristics of the pixel 230.

[0179]FIG. 9A illustrates the angular intensity of the light emitted by
10×10 micron pixels 230 comprising an array of 9×9 uniformly
spaced vertical waveguides 290, having a diameter a as specified above
and center-to-center d=2a, within the meridian plane containing the
diagonal of the pixel at the multiple values of wavelength emitted by the
pixels 230. Specifically, in FIG. 9A the profiles 910, 920 and 930
illustrate the angular intensity of the light emitted by the pixels 230
at the red wavelength (615-nm), the green wavelength (520-nm), and the
blue wavelength (460-nm). As illustrated in FIG. 9A, the multicolor laser
light emitted by the pixel 230, and subsequently the Quantum Photonic
image 200, would have a tightly collimated emission pattern with
collimation angle well within ±5°, thus making the Quantum
Photonic Imager device 200 to have an optical f/# of approximately 4.8.

[0180]The pattern of the vertical waveguides 290 within the pixel 230
surface could be tailored to achieve the required emission
characteristics in terms of the optical f/# for the Quantum Photonic
Imager device 200. The important design criterion in creating the pattern
of the vertical waveguides 290 is to generate a uniform emission at the
required optical f/# while retaining sufficient area for the pixel's
light generating laser diodes 231, 232, and 233 after the array of
vertical waveguides 290 are etched. FIG. 9B illustrates several possible
patterns of the vertical waveguides 290 within the pixel 230 surface that
could be used in conjunction with the Quantum Photonic Imager device 200
of this invention. Based on the teachings of this invention, a person
skilled in the art would know how to select the pattern of the vertical
waveguides 290 within the pixel 230 surface that would generate the light
emission optical f/# that is best suited for the intended application of
the Quantum Photonic Imager device 200 of this invention.

Digital Structure--

[0181]FIG. 10A illustrates a vertical cross-section of the digital
semiconductor structure 220 of the Quantum Photonic Imager device 200.
The digital semiconductor structure 220 would be fabricated with
conventional CMOS digital semiconductor techniques, and as illustrated in
FIG. 10A, would be comprised of the multiple metal layers 222, 223, 224
and 225, separated by thin layers of insulating semiconductor material
such as SiO2, and digital control logic 226 deposited using
conventional CMOS digital semiconductor techniques on the Si-substrate
227.

[0182]As illustrated in FIG. 10B, the metal layer 222 would incorporate a
plurality of pixel's contact pad patterns whereby each contact pad
pattern would be substantially identical to that of the pixel contact pad
pattern of the photonic semiconductor structure 210 illustrated in FIG.
7. The plurality of pixel contact pad patterns of the metal layer 222
would constitute the bonding interface between the photonic semiconductor
structure 210 and the digital semiconductor structure 220 as explained
earlier. The metal layer 222 would also incorporate at its periphery the
device contact bonding pads 221 of the entire Quantum Photonic Imager
device 200 as illustrated in FIG. 2c.

[0183]FIG. 100 illustrates the layout of the metal layer 223 which
incorporate separate power and ground metal rails 310, 315 and 320
designated for distributing power and ground to the pixel's red, green
and blue laser diodes 231, 232, and 233; respectively, and the metal
rails 325 which are designated for routing power and ground to the
digital logic portion of the digital semiconductor structure 220. FIG.
10D illustrates the layout of the metal layer 224 which incorporates
separate metal traces designated for distributing data 410, update 415
and clear 420 signals to the digital control logic semiconductor
structure 226 section designated for controlling the on-off states of the
pixels' red, green and blue laser diodes 231, 232, and 233, respectively.
FIG. 10E illustrates the layout of the metal layer 225 which incorporates
separate metal traces designated for distributing the load 510 and enable
520 signals to the digital control logic semiconductor structure 226
section designated for controlling the on-off states of the pixel's red,
green and blue laser diodes 231, 232, and 233, respectively.

[0184]The digital control logic semiconductor structure 226 would be
comprised of the pixels' digital logic section 228, which is positioned
directly under the photonic semiconductor structure 210 (FIG. 2B), and
the control logic region 229 which is positioned at the periphery of the
digital logic region 228 as illustrated in FIG. 2c. FIG. 11A illustrates
an exemplary embodiment of the control logic section 229 of the digital
control logic semiconductor structure 226, which is designed to accept
red, green and blue PWM serial bit stream input data and clock signals
425, 426, and 427, respectively, which are generated external to the
Quantum Photonic Imager device 200, plus the control clock signals 428
and 429, and covert the accepted data and clock signals into the control
and data signals 410, 415, 420, 510 and 520 which are routed to the
digital logic section 228 via the interconnect metal layers 224 and 225.

[0185]The digital logic section 228 of the digital control logic
semiconductor structure 226 would be comprised of two dimensional arrays
of pixels logic cells 300 whereby each such logic cell would be
positioned directly under one of the pixels 230 comprising the Quantum
Photonic Imager device 200. FIG. 11B illustrates an exemplary embodiment
of the digital logic cell 300 comprising the digital logic section 228 of
the digital control logic semiconductor structure 226. As illustrated in
FIG. 11B, the pixel logic cell 300 associated with each of the pixels
comprising the Quantum Photonic Imager device 200 would be comprised of
the digital logic circuits 810, 815 and 820 corresponding with the red,
green and blue pixel's laser diodes 231, 232, and 233, respectively. As
illustrated in FIG. 11B, the digital logic circuits 810, 815 and 820
would accept the control and data signals 410, 415, 420, 510 and 520 and
based on the accepted data and control signals would enable connectivity
of the power and ground signals 310, 315 and 320 to the red, green and
blue pixel's laser diodes 231, 232, and 233, respectively.

[0186]The digital semiconductor structure 220 would be fabricated as a
monolithic CMOS wafer that would incorporate a multiplicity of digital
semiconductor structures 220 (FIG. 2A). As explained earlier, the digital
semiconductor structure 220 would be bonded with the photonic
semiconductor structure 220 using wafer-level direct bonding techniques
or the like to form an integrated multi wafer structure which would then
be etched at the periphery of each single Quantum Photonic Imager device
200 die area in order to expose the device contact bonding pads 221, then
would be cut into individual Quantum Photonic Imager device 200 dies
illustrated in FIG. 2A and FIG. 2c. Alternatively, the digital
semiconductor 210 wafer would be cut into dies and separately the
photonic semiconductor structure 210 wafer would also be cut into dies,
each having an area that contains the required number of pixel's laser
diodes 231, 232, and 233, and then each the photonic semiconductor
structure 210 die would be die-level bonded using flip-chip techniques or
the like to the digital semiconductor 210 die to form a single Quantum
Photonic Imager device 200 illustrated in FIG. 2A and FIG. 2c.

QPI Fabrication Flow--

[0187]FIG. 12 is a flow chart that illustrates the semiconductor process
flow that would be used to fabricate the Quantum Photonic Imager device
200 in accordance with the exemplary embodiment described in the
preceding paragraphs. As illustrated in FIG. 12, the process starts with
step S02 and continues to step S30, during which various wafers are
bonded, and insulation and metal layers are deposited, interconnect vias,
sidewalls and vertical waveguides are formed. It should be noted that the
semiconductor fabrication flow of the laser diode multilayer
semiconductor structures 250, 260 and 270 as well as the digital
semiconductor structure 220 would be performed separately and external to
the fabrication process flow illustrated in FIG. 12, which is meant to
illustrate an exemplary embodiment of the semiconductor process flow of
bonding these wafers and forming the pixel structures 230 and
interconnects.

[0188]In step S02 the SiO2 insulation layer 241 would be deposited on
the base Si-substrate 240 wafer. In step S04 the p-contact metal layer
would be deposited and in step S06 the formed stack would be bonded with
laser diode multilayer semiconductor wafer and the laser diode wafer is
etched down to the stop-etch layer. In step S08 the pixel sidewalls
trenches are double etched first down to the insulation layer preceding
the metal layers deposited in step S04 then down to the metal layer
deposited in step S04 and the etched trenches are then refilled with
SiO2. In step S10 the trenches for the pixels vertical contact vias
are etched down to the metal layer deposited in step S04 then a thin
insulation layer is deposited and etched to expose the deposited vias. In
step S12 the n-contact metal layer would be deposited then etched to
extend the height of the pixels' sidewall trenches. In step S14 an
insulation layer of SiO2 is deposited then the process flow of steps
S04 through S14 is repeated for each of the laser diode multilayer
semiconductor wafers that would be incorporated into the Quantum Photonic
Imager device 200.

[0189]In step S16 the metal layer required for forming the bonding contact
pad 700 is deposited then etched to form the contact pad pattern
illustrated in FIG. 7. In step S20 the vertical waveguides 290 are etched
through the Si-substrate side of the formed multilayer structure to form
the pixels' 230 waveguide pattern such as those illustrated in FIG. 9B.
In step S22 the waveguide cladding layers 292 are deposited and then the
waveguide cavities are refilled with the waveguide core 291 material in
step S24. In step S26 the Si-substrate side of the formed multi-layer
laser diode structure is polished to optical quality and coated as
required to form the emissive surface of the Quantum Photonic Imager
device 200. Steps S02 through S28 would result in a wafer-size photonic
semiconductor structure 210 which would be wafer-level pad-side bonded
with the digital semiconductor structure 220 wafer in step S28.

[0190]In step S30 the resultant multi-wafer stack is etched to expose the
contact pads 221 of the individual dies Quantum Photonic Imager device
200 and the multi-wafer stack is cut into individual dies of the Quantum
Photonic Imager device 200.

[0191]An alternative approach to the process of step S30 would be to cut
the photonic semiconductor structure 210 formed by the process steps S02
through S26 into the die size required for the Quantum Photonic imager
device 200 and separately cut the digital semiconductor structure 220
wafer into dies then pad-side bond the two dies using flip-chip technique
to form the individual dies of the Quantum Photonic Imager device 200.

QPI Projector--

[0192]The Quantum Photonic Imager device 200 would typically be used as a
digital image source in digital image projectors used in front or rear
projection display systems. FIG. 13 illustrates an exemplary embodiment
of a typical digital image projector 800 that incorporates the Quantum
Photonic Imager device 200 of this invention as a digital image source.
The Quantum Photonic Imager device 200 would be integrated on a printed
circuit board together with a companion digital device 850 (which will be
referred to as the image data processor and will be functionally
described in subsequent paragraphs) that would be used convert the
digital image input into the PWM formatted input to the Quantum Photonic
Imager device 200. As illustrated in FIG. 13, the emissive optical
aperture of the Quantum Photonic Imager device 200 would be coupled with
a projection optics lens group 810 which would magnify the image
generated by the Quantum Photonic Imager device 200 to the required
projection image size.

[0193]As explained earlier, the light emitted from Quantum Photonic Imager
device 200 would typically be contained within an optical f/# of
approximately 4.8, which makes it possible to use few lenses (typically 2
or 3 lenses) of moderate complexity to achieve source image magnification
in the range between 20 to 50. Typical digital projectors that use
existing digital imagers such as micro-mirror, LCOS or HTPS imager
devices having an optical f/# of approximately 2.4, would typically
requires as many as 8 lenses to achieve a comparable level of source
image magnification. Furthermore, typical digital projectors that use
passive (meaning reflective or transmissive type) digital imagers such as
micro-mirror, LCOS or HTPS imager devices would require a complex optical
assembly to illuminate the imager. In comparison, since the Quantum
Photonic Imager device 200 is an emissive imager, the digital image
projector 800 which uses the Quantum Photonic Imager device 200 would not
require any complex optical illumination assembly. The reduced number of
lenses required for magnification plus the elimination of the
illumination optics would make the digital image projector 800 which uses
the Quantum Photonic Imager device 200 substantially less complex and
subsequently more compact and less costly than digital projectors that
use existing digital imagers such as micro-mirror, LCOS or HTPS imager
devices.

OPI Device Efficiency--

[0194]An important aspect of the Quantum Photonic Imager device 200 of
this invention is its luminance (brightness) performance and its
corresponding power consumption. A single 10×10 micron pixel 230
having the laser diode structures 231, 232, and 233 of the preceding
exemplary embodiment as specified in FIG. 4A, FIG. 4B and FIG. 4C,
respectively, would consume approximately 4.5 μW, 7.4 μW and 11.2
μW to generate a radiant flux of approximately 0.68 μW, 1.1 μW
and 1.68 μW of red (615-nm), green (520-nm) and blue (460-nm);
respectively, which equates to 1 milli lumen of luminous flux at color
temperature of 8,000 K°. In other words, the single 10×10
micron pixel 230 of the Quantum Photonic Imager device 200 would consume
approximately 23 μW to generate approximately 1 milli lumen of
luminous flux at color temperature of 8,000 K°, which would be
sufficient to provide a brightness of more than 1,200 candela/meter2
when the pixel is magnified to 0.5×0.5 millimeter. At the
brightness provided by most existing commercial displays, which typically
ranges between 350 candela/meter2 to 500 candela/meter2, the
single 10×10 micron pixel 230 of the Quantum Photonic Imager device
200 when magnified in size to 0.5×0.5 millimeter would consume less
than 10 μW, which is nearly one and a half orders of magnitude less
than the power consumption required by existing commercial displays such
as PDP, LCD or projection displays that use a micro-mirrors, LCOS or HTPS
devices.

[0195]As a direct result of the elimination of the inefficiencies
associated with illumination optics and the imager optical coupling
required in all projectors that use existing digital imagers such as
micro-mirror, LCOS or HTPS imager devices, the Quantum Photonic Imager
device 200 of this invention would achieve substantially higher
efficiency when compared to existing digital imagers. Specifically, the
losses associated with the digital projector 800 illustrated in FIG. 13
that uses the Quantum Photonic Imager 200 of this invention would be
limited to the losses due to projection optics lens group 810, which
would approximately be about 4%. Meaning that the efficiency of the
digital projector 800 illustrated in FIG. 13 that uses the Quantum
Photonic Imager 200 in terms of the ratio of projected luminous flux to
the generated luminous flux would be approximately 96%, which is
substantially higher than the efficiency of less than 10% achieved by
projectors that use existing digital imagers such as micro-mirror, LCOS
or HTPS imager devices.

[0196]For example, the digital projector 800 illustrated in FIG. 13 that
uses the Quantum Photonic Imager 200 of this invention having one million
pixels would consume approximately 25.4 watts to generate approximately
1,081 lumens of luminous flux at color temperature of 8,000 K°,
which would be sufficient to project an image having 60'' diagonal at a
brightness of approximately 1,000 candela/meter2 on a front
projection screen. When the efficiency of a typical projection screen is
taking into account, the cited example of the digital projector 800 would
project an image with brightness of approximately 560 candela/meter2
on a rear projection screen. For comparison purposes the power
consumption of a typical existing rear projection displays that achieve
brightness in the range of 350 candela/meter2 would be in excess of
250 watts, which indicates that the digital projector 800 that uses the
Quantum Photonic Imager 200 as an image source would achieve a much
higher projected image brightness than existing front and rear projection
displays, yet at a substantially lower power consumption.

OPI Advantages & Applications--

[0197]The compactness and low cost characteristics of the digital image
projector 800 which uses the Quantum Photonic Imager device 200 when
combined with the low power consumption of the Quantum Photonic Imager
device 200 would make it possible to design and fabricate digital image
projectors that can be effectively embedded in mobile platforms such as
cell phones, laptop PC or comparable mobile devices. In particular, the
digital projector 800 that uses the Quantum Photonic Imager 200 of this
invention such as that illustrated in FIG. 13 having 640×480 pixels
and designed to achieve ±25 degrees projection field of view would
achieve approximately 15×15 mm volume and would consume less than
1.75 watts to project 18'' projected image diagonal with brightness of
approximately 200 candela/meter2 (for reference purposes, the
typical brightness of a laptop PC is approximately 200
candela/meter2).

[0198]Because of its compactness and low power consumption, the Quantum
Photonic Imager 200 of the invention would also be suitable for near-eye
applications such as helmet-mounted displays and visor displays.
Furthermore, because of its ultra-wide gamut capabilities, the Quantum
Photonic Imager 200 of the invention would also suitable for applications
requiring realistic image color rendition such as simulator displays and
gaming displays.

QPI Operation--

[0199]With its pixel-based laser light generating capabilities described
in the preceding paragraphs, the Quantum Photonic Imager device 200 will
be able to convert the digital source image data received from an
external input into an optical image which would be coupled into the
projection optics of the projector 800 as illustrated in FIG. 13. In
using the Quantum Photonic Imager device 200 of this invention to
synthesize the source image, the luma (brightness) and chroma (color)
components of each of the image pixels would be simultaneously
synthesized through apportioned setting of the on/off duty cycle of the
corresponding pixel's red, green and blue laser diodes 231, 232, and 233.
Specifically, for each of the source image pixels, the chroma component
of the pixel would be synthesized by setting the corresponding pixel's
red, green and blue laser diodes 231, 232, and 233 on/off duty cycle
relative ratios that reflect the required color coordinates for the
pixel. Similarly, for each of the source image pixels, the luma component
of the pixel would be synthesized by setting the on/off duty cycle of the
corresponding pixel's light generating red, green and blue laser diodes
231, 232, and 233 collective on/off duty cycle values that reflect the
required brightness for the pixel. In other words, the pixel's luma and
chroma components of each of the source image pixels would be synthesized
by controlling the on/off duty cycle and the simultaneity of the
corresponding pixel's light generating red, green and blue laser diodes
231, 232, and 233 of the Quantum Photonic Imager device 200.

[0200]By controlling the on/off duty cycle and simultaneity of the pixel's
laser diodes 231, 232, and 233 having the selected wavelengths of the
exemplary embodiment of the Quantum Photonic Imager device 200 described
in the preceding paragraphs of 615-nm for the pixel's red laser diodes
231, 520-nm for the pixel's green laser diode 232, and 460-nm for the
pixel's blue laser diode 233, the Quantum Photonic Imager device 200 of
this invention would be able to synthesize any pixel's color coordinate
within its native color gamut 905 illustrated in FIG. 14A in reference to
the CIE XYZ color space. Specifically, the aforementioned operational
wavelengths of the exemplary embodiment of the Quantum Photonic Imager
device 200 pixel's laser diodes 231, 232, and 233 would define the
vertices 902, 903 and 904; respectively, of its native color gamut 905 as
illustrated in FIG. 14A in reference to the CIE XYZ color space.

[0201]The specific color gamut of the source image would typically be
based on image color standards such as NTSC and HDTV standards. For
comparison purposes, the display color gamut standards of NTSC 308 and
HDTV 309 are also shown on FIG. 14A as a reference to illustrate that the
native color gamut 305 of the exemplary embodiment the Quantum Photonic
Imager device 200 defined by the color primaries wavelengths for red at
615-nm, green at 520-nm and blue at 460-nm would include the NTSC 308 and
HDTV 309 color gamut standards and would extend beyond these color gamut
standards by a significant amount.

[0202]Given the extended native color gamut 305 of the Quantum Photonic
Imager device 200 illustrated in FIG. 14A, the source image data would
have to be mapped (converted) from its reference color gamut (such as
that illustrated in FIG. 14A for the NTSC 308 and the HDTV 309 color
gamut) to the native color gamut 305 of the Quantum Photonic Imager
device 200. Such a color gamut conversion would be accomplished by
applying the following matrix transformation on the [ft G, and B]
components of each of the source image pixels:

[ R QPI G QPI B QPI ] = M [ R G B
] ( 6 ) ##EQU00001##

Where the 3×3 transformation matrix M would be computed from the
chromaticity values of the coordinates of the white point and color
primaries of the source image color gamut and the coordinates of the
white point and color primaries 902, 903 and 904 (FIG. 14B) of the
Quantum Photonic Imager device 200 within a given the reference color
space, such as CIE XYZ color space for example. The result of the matrix
transformation defined by Equation (6) would define the components of the
source image pixel [RQPI, GQPI, BQPI] with respect to the
native color gamut 305 of the Quantum Photonic Imager device 200.

[0203]FIG. 14B illustrates the result of the matrix transformation defined
by Equation (6) to define the components of the source image pixel
[RQPI, GQPI, BQPI] of two exemplary pixels 906 and 907
with respect to the Quantum Photonic Imager device 200 native color gamut
305 defined by the vertices 902, 903 and 904. As illustrated in FIG. 14B,
the values [RQPI, GQPI, BQPI] could span the entire color
gamut 305, enabling the Quantum Photonic Imager device 200 to synthesize
the pixels [R,G,B] values of a source image that have a much wider color
gamut than that offered by the NTSC 308 and the HDTV 309 color gamut
(FIG. 14A). As wider color gamut standards and wide-gamut digital image
and video input content becomes available, digital projectors 800 that
use the Quantum Photonic Imager 200 of this invention would be poised to
project source images and video content in such wide-gamut format. In the
interim, the wide-gamut capabilities of the Quantum Photonic Imager 200
would allow it to synthesize digital image and video inputs with the
existing color gamut (such as NTSC 308 and the HDTV 309 color gamut) at
an even lower power consumption than the exemplary values cited in an
earlier paragraph.

[0204]The [R, G, B] values of every pixel in the source image would be
mapped (converted) to the native color gamut 305 (color space) of the
Quantum Photonic Imager device 200 using the transformation defined by
Equation (6). Without loss of generality, in assuming that the white
point of the source image has an [R,G,B]=[1, 1, 1], a condition which can
always be met by dividing [R,G,B] values of every pixel in the source
image by the white point's [R,G,B] value, the result of the
transformation defined by Equation (6) for each of the source image
pixels would be a vector [RQPI, GQPI, BQPI] with values
ranging between [0, 0, 0] for black and [1, 1, 1] for white. The above
representation has the benefit that the distances within the reference
color space, such as CIE XYZ color space for example, between the pixel's
and the color primaries 902, 903 and 904 of the native gamut 305 of the
Quantum Photonic Imager device 200 defined by the values [RQPI,
GQPI, BQPI] would also define the on/off duty cycles values for
its respective red, green, and blue laser diodes 231, 232, and 233:

λR=RQPI

λG=GQPI

λB=BQPI (7)

Where λR, λG, and λB denote the on/off
duty cycles of the respective pixel 230 of the Quantum Photonic Imager
device 200 red, green, and blue laser diodes 231, 232, and 233;
respectively, required to synthesize [R,G,B] values of each of the pixels
comprising the source image.

[0205]Typical source image data input, whether static images or dynamic
video images, would be comprised of image frames which are inputted at a
frame rate, for example either 60 Hz or 120 Hz. For a given source image
frame rate, the on-time of the respective pixel 230 of the Quantum
Photonic Imager device 200 red, green, and blue laser diodes 231, 232,
and 233; respectively, required to synthesize the [R,G,B] values of
source image pixel would be the fraction of the frame duration defined by
the values λR, λG, and λB.

[0206]In order to account for possible pixel-to-pixel brightness
variations that could result from possible variations in the
semiconductor material characteristics comprising the photonic
semiconductor structure 210, during testing of the Quantum Photonic
Imager device 200 which would typically occur at the completion of the
device fabrication steps described earlier, the device luminance profile
would be measured and a brightness uniformity weighting factor would be
calculated for each pixel. The brightness uniformity weighting factors
would be stored as a look-up-table (LUT) and applied by the Quantum
Photonic Imager device 200 companion image data processor 850. When these
brightness uniformity weighting factors are taken into account, the
on-time for each of the pixel 230 of the Quantum Photonic Imager device
200 would be given by:

ΛR=KRλR

ΛG=KGλG

ΛB=KBλB (8)

Where KR, KG and KB are the brightness uniformity weighting
factors for each of the Quantum Photonic Imager device 200 pixel's red,
green, and blue laser diodes 231, 232, and 233; respectively.

[0207]The on-time values of the red, green, and blue laser diodes 231,
232, and 233 of each of the pixels 230 comprising the Quantum Photonic
Imager device 200 expressed by Equation (8) would be converted into
serial bit streams using conventional pulse width modulation (PWM)
techniques and inputted to the Quantum Photonic Imager device 200 at the
frame rate of the source image together with the pixel address (row and
column address of the respective pixel within the array of pixels
comprising the Quantum Photonic Imager device 200) and the appropriate
synchronization clock signals.

[0208]The conversion of the image source data into the input signals
required by the Quantum Photonic Imager device 200 would be performed by
the companion image data processor 850 in accordance with Equations (6)
through (8). FIG. 15A and FIG. 15B illustrate a block diagram of the
Quantum Photonic image data processor 850 and the timing diagram
associated with its interface with the Quantum Photonic Imager device
200; respectively. Referring to FIG. 15A and FIG. 15B, the SYNC & Control
block 851 would accept the frame synchronization input signal 856
associated with the source image or video input and generate the frame
processing clock signal 857 and the PWM clock 858. The PWM clock 858 rate
would be dictated by the frame rate and word length of the source image
or video input. The PWM clock 858 rate illustrated in FIG. 15B reflects
an exemplary embodiment of the Quantum Photonic Imager 200 and companion
Image Data Processor 850 operating at a frame rate of 120 Hz and word
length of 16-bit. A person skilled in the art would know how to use the
teachings of this invention to make the Quantum Photonic Imager 200 and
its companion Image data Processor 850 support source image or video
inputs having frame rates and word lengths that differ from those
reflected in FIG. 15B.

[0209]In synchronism with the frame clock signal 857, the Color-Space
Conversion block 852 would receive each frame of the source image or
video data, and using the source input gamut coordinates, would perform
the digital processing defined by Equations (6) to map each of the source
input pixel [R,G,B] values to the pixel coordinate values [RQPI,
GQPI, BQPI]. Using the white-point coordinates of the source
image or video data input, the Color-Space Conversion block 852 would
then convert each of the pixel values [RQPI, GQPI, BQPI]
using Equation (7) to the on/off duty cycle values λR,
λG, and λB of the red, green, and blue laser diodes
231, 232, and 233, respectively, of the corresponding pixel 230 of
Quantum Photonic Imager 200.

[0210]The values λR, λG, and λB would
then be used by the Uniformity Correction block 853 in conjunction with
the pixel brightness weighting factor KR, KG and KB stored
in the Uniformity Profile LUT 854 to generate the uniformity corrected
on-time values [ΛR, ΛG, θB] for each
of the pixels 230 of the Quantum Photonic Imager 200 using equation (8).

[0211]The values [ΛR, ΛG, ΛB]
generated by the Uniformity Correction block 853, which would typically
be expressed in three 16-bit words for each pixel, are then converted by
the PWM Conversion block 855 into a three serial bit streams that would
be provided to the Quantum Photonic Imager 200 in synchronism with the
PWM clock. The three PWM serial bit streams generated by the PWM
Conversion block 855 for each of the pixels 230 would provide the Quantum
Photonic Imager device 200 with 3-bit words, each of which define the
on-off state of the pixel's light generating red, green and blue laser
diodes 231, 232, and 233 within the duration of the PWM clock signal 858.
The 3-bit word generated by the PWM Conversion block 855 would be loaded
into the appropriate pixel address of the digital semiconductor structure
220 of the Quantum Photonic Imager device 200 and would be used, as
explained earlier, to turn on or off the respective pixel's red, green
and blue laser diodes 231, 232, and 233 within the duration defined by
the PWM clock signal 858.

[0212]In the preceding exemplary embodiment of the operation of the
Quantum Photonic Imager device 200 of this invention, the source image
pixels color and brightness specified by the pixel [ft G, B] values would
be directly synthesized for each individual pixel in the source image
using the color primaries 902, 903 and 904 of the native gamut 305 of the
Quantum Photonic Imager device 200. Because the individual pixel
brightness and color are directly synthesized, this operational mode of
the Quantum Photonic Imager device 200 is referred to as Direct-Color
Synthesize Mode. In an alternative exemplary embodiment of the operation
of the Quantum Photonic Imager device 200 the color primaries of the
source image color gamut are first synthesized using the color primaries
902, 903 and 904 of the native gamut 305 of the Quantum Photonic Imager
device 200 and the pixel color and brightness are then synthesized using
the synthesized color primaries of the source image color gamut. In this
operational mode of the Quantum Photonic Imager device 200, the pixel's
red, green and blue laser diodes 231, 232, and 233 collectively would
sequentially synthesize the RGB color primaries of the source image. This
would be accomplished by dividing the frame duration into three segments
whereby each segment would be dedicated for generating one of the color
primaries of the source image and having the default values (white-point)
of each of the pixel's red, green and blue laser diodes 231, 232, and 233
reflect the coordinates of one of the source image color primaries in
each of the frame segments sequentially. The duration of the frame
dedicated to each color primary segment and the relative on-time values
of the pixel's red, green and blue laser diodes 231, 232, and 233 during
that segment would be selected based on the required white-point color
temperature. Because the individual pixel brightness and color are
sequentially synthesized, this operational mode of the Quantum Photonic
Imager device 200 is referred to as Sequential-Color Synthesize Mode.

[0213]In the Sequential-Color Synthesize Mode of the Quantum Photonic
Imager device 200, the total number of PWM clock cycles within the frame
would be apportioned into three color primaries sub-frames, with one
sub-frame dedicated to the R-primary, the second dedicated for the
G-primary and the third dedicated for the B-primary of the source image
gamut. The on-time of each the Quantum Photonic Imager device 200 pixel's
red, green and blue laser diodes 231, 232, and 233 during the R-primary
sub-frame, G-primary sub-frame and the B-primary sub-frame would be
determined based on the distances within the reference color space
between the source image color primaries and the color primaries of the
Quantum Photonic Imager device 200 native color gamut. These on-time
values would then be modulated sequentially with [ft G, and B] values of
the respective pixel of the source image.

[0214]The difference between Direct-Color Synthesize mode and
Sequential-Color Synthesize mode of the Quantum Photonic Imager device
200 is illustrated in FIG. 15B which shows the enable signal that would
be provided to the pixel's red, green and blue laser diodes 231, 232, and
233 in each case. The sequence of enable signals 860 illustrate the
operation of the pixel's red, green and blue laser diodes 231, 232, and
233 in the Direct-Color Synthesize mode where the pixel's luma and chroma
components of the source image pixels would be directly synthesized by
controlling the on/off duty cycle and simultaneity of the corresponding
pixel's red, green and blue laser diodes 231, 232, and 233. The sequence
of enable signals 870 illustrate the operation of the pixel's red, green
and blue laser diodes 231, 232, and 233 in the Sequential-Color
Synthesize mode where the primaries of the source image gamut would be
synthesized using the color primaries 902, 903 and 904 of the native
gamut 305 and luma and chroma components of the source image pixels would
be synthesized sequentially using the synthesized primaries of the source
image gamut.

[0215]The Direct-Color Synthesize mode and Sequential-Color Synthesize
mode of the Quantum Photonic Imager device 200 would differ in terms of
the achieved operating efficiency of the device as they would tend to
require different peak-to-average power driving conditions to achieve
comparable level image brightness. However in both operational modes the
Quantum Photonic Imager device 200 of this invention would be able to
support comparable source image frame rate and [ft G, B] word length.

QPI Dynamic Range, Response Time, Contrast and Black Level--

[0216]The dynamic range capability of the Quantum Photonic Imager device
200 (defined as the total number of grayscale levels that can be
generated in the synthesize for each of the source image pixels) would be
determined by the smallest value of PWM clock duration that can be
supported, which in turn would be determined by the on-off switching time
of the pixel's red, green and blue laser diodes 231, 232, and 233. The
exemplary embodiment of the photonic semiconductor structure 210 (FIG.
2A) described in the preceding paragraphs would achieve on-off switching
time that is a fraction of a nanosecond in duration, making the Quantum
Photonic Imager device 200 able to readily achieve a dynamic range of
16-bit. For comparison, most currently available display systems operate
at 8-bit dynamic. Furthermore, the on-off switching time of a fraction of
a nanosecond in duration that can be achieved by the photonic
semiconductor structure 210 would also enable of the Quantum Photonic
Imager device 200 to achieve a response time that is a fraction of a
nanosecond in duration. For comparison, the response time that can be
achieved by LCoS and HTPS type imagers is typically in the order of 4 to
6 milliseconds and that of the micro mirror type imager is typically in
the order of one microsecond. The imager response time plays a critical
role in the quality of the image that can be generated by the display
system, in particular for generating video images. The relatively slow
response time of the LCoS and HTPS type imagers would tend to create
undesirable artifacts in the generated video image.

[0217]The quality of a digital display is also measured by the contrast
and black level it can generate, with the contrast being a measure of the
relative levels of white and black regions within the image and black
level being the maximum black that can be achieved in response to a black
filed input. Both the contrast and the black level of a display are
significantly degraded in existing projection displays that use imagers
such as micro mirror, LCoS or HTPS imager because of the significant
levels of photonic leakage associated with such imagers. The high
photonic leakage typical to these types of imager is caused by light
leaking from the on-state of the imager pixel onto its off-state, thus
causing the contrast and black levels to degrade. This effect is more
pronounced when such imagers are operated in a color sequential mode. In
comparison the Quantum Photonic Imager device 200 would have no photonic
leakage since its pixel's red, green and blue laser diodes 231, 232, and
233 on-state and off-states are substantially mutually exclusive making,
the contrast and black levels that can be achieved by the Quantum
Photonic Imager device 200 orders of magnitude superior to what can be
achieved by micro mirror, LCoS or HTPS imagers.

[0218]In summary, the Quantum Photonic Imager device 200 of the present
invention overcomes the weaknesses of other imagers plus exhibits the
following several advantages:

[0219]1. It requires low power consumption because of its high efficiency;

[0220]2. It reduces the overall size and substantially reduces the cost of
the projection system because it requires simpler projection optics and
does not require complex illumination optics;

[0221]3. It offers extended color gamut making it is able to support the
wide-gamut requirements of the next generation display systems; and

[0222]4. It offers fast response time, extended dynamic range, plus high
contrast and black levels, which collectively would substantially improve
the quality of the displayed image.

[0223]In the forgoing detailed description, the present invention has been
described with reference to specific embodiments thereof. It will,
however, be evident that various modifications and changes can be made
thereto without departing from the broader spirit and scope of the
invention. The design details and drawings are, accordingly, to be
regarded in an illustrative rather than a restrictive sense. Skilled
persons will recognize that portions of this invention may be implemented
differently than the implementation described above for the preferred
embodiment. For example, skilled persons will appreciate that the Quantum
Photonic Imager device 200 of this invention can be implemented with
numerous variations to the number of multilayer laser diodes comprising
the photonic semiconductor structure 210, the specific design details of
the multilayer laser diodes 250, 260 and 270, the specific design details
of the vertical waveguides 290, specific design details associated with
the selection of the specific pattern of the pixel's vertical waveguides
290, the specific details of the semiconductor fabrication procedure, the
specific design details of the projector 800, the specific design details
of the companion Image Data Processor device 850, the specific design
details of the digital control and processing required for coupling the
image data input to the Quantum Photonic device 200, and the specific
design details associated with the selected operational mode of the
chip-set comprising the Quantum Photonic Imager 200 and its companion
Image Data Processor 850. Skilled persons will further recognize that
many changes may be made to the details of the aforementioned embodiments
of this invention without departing from the underlying principles and
teachings thereof. The scope of the present invention should, therefore,
be determined only by the following claims.